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• Trouble deciding how to add popup menu to eclipse plugin using either action ObjectContributions or command handlers

  - by user1808408

  The issue is this: Most things I read on the web says that we should avoid actions when creating popup menus because the command framework allows for more decoupling. Example: http://wiki.eclipse.org/FAQ_What_is_the_difference_between_a_command_and_an_action%3F Fair enough. But I am having a heck of a time getting the command framework to add my menu when I right click on a .java file inside the editor, and only when I click inside the editor. I can get the menu to show (using 'with' and the activeEditor variable), but it also shows when I right click on the java file inside the package explorer, which I don't want. I suspect it's because the file is already open inside the editor. I also have a menu that gets added when I right click on the java file inside the package explorer, using IComplilationUnit. That works fine. So my problem is solved using a popup menu action for when I click inside the file. I also get access to to all the ISelection stuff there. But the coupling is to high and I lose the flexability of using handlers. I'm looking for either: Tell me I'm doing it the only way possible; or Tell me how to have my popup appear only when I right click on the java file editor. Regards

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• data ownership and performance

  - by Ami

  We're designing a new application and we ran into some architectural question when thinking about data ownership. we broke down the system into components, for example Customer and Order. each of this component/module is responsible for a specific business domain, i.e. Customer deals with CRUD of customers and business process centered around customers (Register a n new customer, block customer account, etc.). each module is the owner of a set of database tables, and only that module may access them. if another module needs data that is owned by another module, it retrieves it by requesting it from that module. so far so good, the question is how to deal with scenarios such as a report that needs to show all the customers and for each customer all his orders? in such a case we need to get all the customers from the Customer module, iterate over them and for each one get all the data from the Order module. performance won't be good...obviously it would be much better to have a stored proc join customers table and orders table, but that would also mean direct access to the data that is owned by another module, creating coupling and dependencies that we wish to avoid. this is a simplified example, we're dealing with an enterprise application with a lot of business entities and relationships, and my goal is to keep it clean and as loosely coupled as possible. I foresee in the future many changes to the data scheme, and possibly splitting the system into several completely separate systems. I wish to have a design that would allow this to be done in a relatively easy way. Thanks!

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• Sharing class member data between sub components

  - by Tim Gradwell

  I have an aggregate 'main' class which contains some data which I wish to share. The main class also has other class members. I want to share the data with these other class members. What is the correct / neatest way to do this? The specific example I have is as follows. The main class is a .net Form. I have some controls (actually controls within controls) on the main form which need access to the shared data. Main Form - DataX - DataY - Control1 -- Subcontrol1 - Control2 -- SubControl2 SubControls 1 and 2 both wish to access DataX and DataY. The trouble is, I feel like better practice (to reduce coupling), would be that either subcontrols should not know about Main Form, or Main Form should not know about subcontrols - probably the former. For subcontrols not to know about Main Form, would probably mean Main Form passing references to both Controls 1 and 2, which in turn would pass the references on to SubControls 1 and 2. Lots of lines of code which just forward the references. If I later added DataZ and DataW, and Controls 3 and 4 and SubControls 3 and 4, I'd have to add lots more reference forwarding code. It seems simpler to me to give SubControls 1 and 2 member references to Main Form. That way, any sub control could just ask for MainForm.DataX or MainForm.DataY and if I ever added new data, I could just access it directly from the sub controls with no hassle. But it still involves setting the 'MainForm' member references every time I add a new Control or Subcontrol. And it gives me a gut feeling of 'wrong'. As you might be able to tell I'm not happy with either of my solutions. Is there a better way? Thanks

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• When my object is no longer referenced why do its events continue to run?

  - by Ryan Peschel

  Say I am making a game and have a base Buff class. I may also have a subclass named ThornsBuff which subscribes to the Player class's Damaged event. The Player may have a list of Buffs and one of them may be the ThornsBuff. For example: Test Class Player player = new Player(); player.ActiveBuffs.Add(new ThornsBuff(player)); ThornsBuff Class public ThornsBuff(Player player) { player.DamageTaken += player_DamageTaken; } private void player_DamageTaken(MessagePlayerDamaged m) { m.Assailant.Stats.Health -= (int)(m.DamageAmount * .25); } This is all to illustrate an example. If I were to remove the buff from the list, the event is not detached. Even though the player no longer has the buff, the event is still executed as if he did. Now, I could have a Dispel method to unregister the event, but that forces the developer to call Dispel in addition to removing the Buff from the list. What if they forget, increased coupling, etc. What I don't understand is why the event doesn't detatch itself automatically when the Buff is removed from the list. The Buff only existed in the list and that is its one reference. After it is removed shouldn't the event be detached? I tried adding the detaching code to the finalizer of the Buff but that didn't fix it either. The event is still running even after it has 0 references. I suppose it is because the garbage collector had not run yet? Is there any way to make it automatic and instant so that when the object has no references all its events are unregisted? Thanks.

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• Windows Azure Use Case: Hybrid Applications

  - by BuckWoody

  This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Organizations see the need for computing infrastructures that they can “rent” or pay for only when they need them. They also understand the benefits of distributed computing, but do not want to create this infrastructure themselves. However, they may have considerations that prevent them from moving all of their current IT investment to a distributed environment: Private data (do not want to send or store sensitive data off-site) High dollar investment in current infrastructure Applications currently running well, but may need additional periodic capacity Current applications not designed in a stateless fashion In these situations, a “hybrid” approach works best. In fact, with Windows Azure, a hybrid approach is an optimal way to implement distributed computing even when the stipulations above do not apply. Keeping a majority of the computing function in an organization local while exploring and expanding that footprint into Windows and SQL Azure is a good migration or expansion strategy. A “hybrid” architecture merely means that part of a computing cycle is shared between two architectures. For instance, some level of computing might be done in a Windows Azure web-based application, while the data is stored locally at the organization. Implementation: There are multiple methods for implementing a hybrid architecture, in a spectrum from very little interaction from the local infrastructure to Windows or SQL Azure. The patterns fall into two broad schemas, and even these can be mixed. 1. Client-Centric Hybrid Patterns In this pattern, programs are coded such that the client system sends queries or compute requests to multiple systems. The “client” in this case might be a web-based codeset actually stored on another system (which acts as a client, the user’s device serving as the presentation layer) or a compiled program. In either case, the code on the client requestor carries the burden of defining the layout of the requests. While this pattern is often the easiest to code, it’s the most brittle. Any change in the architecture must be reflected on each client, but this can be mitigated by using a centralized system as the client such as in the web scenario. 2. System-Centric Hybrid Patterns Another approach is to create a distributed architecture by turning on-site systems into “services” that can be called from Windows Azure using the service Bus or the Access Control Services (ACS) capabilities. Code calls from a series of in-process client application. In this pattern you move the “client” interface into the server application logic. If you do not wish to change the application itself, you can “layer” the results of the code return using a product (such as Microsoft BizTalk) that exposes a Web Services Definition Language (WSDL) endpoint to Windows Azure using the Application Fabric. In effect, this is similar to creating a Service Oriented Architecture (SOA) environment, and has the advantage of de-coupling your computing architecture. If each system offers a “service” of the results of some software processing, the operating system or platform becomes immaterial, assuming it adheres to a service contract. There are important considerations when you federate a system, whether to Windows or SQL Azure or any other distributed architecture. While these considerations are consistent with coding any application for distributed computing, they are especially important for a hybrid application. Connection resiliency - Applications on-premise normally have low-latency and good connection properties, something you’re not always guaranteed in a distributed and hybrid application. Whether a centralized client or a distributed one, the code should be able to handle extended retry logic. Authorization and Access - In a single authorization environment like a Active Directory domain, security is handled at a user-password level. In a distributed computing environment, you have more options. You can mitigate this with  using The Windows Azure Application Fabric feature of ACS to make the Azure application aware of the App Fabric as an ADFS provider. However, a claims-based authentication structure is often a superior choice.  Consistency and Concurrency - When you have a Relational Database Management System (RDBMS), Consistency and Concurrency are part of the design. In a Service Architecture, you need to plan for sequential message handling and lifecycle. Resources: How to Build a Hybrid On-Premise/In Cloud Application: http://blogs.msdn.com/b/ignitionshowcase/archive/2010/11/09/how-to-build-a-hybrid-on-premise-in-cloud-application.aspx  General Architecture guidance: http://blogs.msdn.com/b/buckwoody/archive/2010/12/21/windows-azure-learning-plan-architecture.aspx   

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• Integrating Code Metrics in TFS 2010 Build

  - by Jakob Ehn

  The build process template and custom activity described in this post is available here: http://cid-ee034c9f620cd58d.office.live.com/self.aspx/BlogSamples/CodeMetricsSample.zip Running code metrics has been available since VS 2008, but only from inside the IDE. Yesterday Microsoft finally releases a Visual Studio Code Metrics Power Tool 10.0, a command line tool that lets you run code metrics on your applications.  This means that it is now possible to perform code metrics analysis on the build server as part of your nightly/QA builds (for example). In this post I will show how you can run the metrics command line tool, and also a custom activity that reads the output and appends the results to the build log, and also fails he build if the metric values exceeds certain (configurable) treshold values. The code metrics tool analyzes all the methods in the assemblies, measuring cyclomatic complexity, class coupling, depth of inheritance and lines of code. Then it calculates a Maintainability Index from these values that is a measure f how maintanable this method is, between 0 (worst) and 100 (best). For information on hwo this value is calculated, see http://blogs.msdn.com/b/codeanalysis/archive/2007/11/20/maintainability-index-range-and-meaning.aspx. After this it aggregates the information and present it at the class, namespace and module level as well. Running Metrics.exe in a build definition Running the actual tool is easy, just use a InvokeProcess activity last in the Compile the Project sequence, reference the metrics.exe file and pass the correct arguments and you will end up with a result XML file in the drop directory. Here is how it is done in the attached build process template: In the above sequence I first assign the path to the code metrics result file ([BinariesDirectory]\result.xml) to a variable called MetricsResultFile, which is then sent to the InvokeProcess activity in the Arguments property. Here are the arguments for the InvokeProcess activity: Note that we tell metrics.exe to analyze all assemblies located in the Binaries folder. You might want to do some more intelligent filtering here, you probably don’t want to analyze all 3rd party assemblies for example. Note also the path to the metrics.exe, this is the default location when you install the Code Metrics power tool. You must of course install the power tool on all build servers. Using the standard output logging (in the Handle Standard Output/Handle Error Output sections), we get the following output when running the build: Integrating Code Metrics into the build Having the results available next to the build result is nice, but we want to have results integrated in the build result itself, and also to affect the outcome of the build. The point of having QA builds that measure, for example, code metrics is to make it very clear how the code being built measures up to the standards of the project/company. Just having a XML file available in the drop location will not cause the developers to improve their code, but a (partially) failing build will! To do this, we need to write a custom activity that parses the metrics result file, logs it to the build log and fails the build if the values frfom the metrics is below/above some predefined treshold values. The custom activity performs the following steps Parses the XML. I’m using Linq 2 XSD for this, since the XML schema for the result file is available, it is vey easy to generate code that lets you query the structure using standard Linq operators. Runs through the metric result hierarchy and logs the metrics for each level and also verifies maintainability index and the cyclomatic complexity with the treshold values. The treshold values are defined in the build process template are are sent in as arguments to the custom activity If the treshold values are exceeded, the activity either fails or partially fails the current build. For more information about the structure of the code metrics result file, read Cameron Skinner's post about it. It is very simpe and easy to understand. I won’t go through the code of the custom activity here, since there is nothing special about it and it is available for download so you can look at it and play with it yourself. The treshold values for Maintainability Index and Cyclomatic Complexity is defined in the build process template, and can be modified per build definition: I have taken the default value for these settings from my colleague Terje Sandström post on Code Metrics - suggestions for approriate limits. You’ll notice that this is quite an improvement compared to using code metrics inside the IDE, where Red/Yellow/Green limits are fixed (and the default values are somewaht strange, see Terjes post for a discussion on this) This is the first version of the code metrics integration with TFS 2010 Build, I will proabably enhance the functionality and the logging (the “tree view” structure in the log becomes quite hard to read) soon. I will also consider adding it to the Community TFS Build Extensions site when it becomes a bit more mature. Another obvious improvement is to extend the data warehouse of TFS and push the metric results back to the warehouse and make it visible in the reports.

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• Getting to grips with the stack in nasm

  - by MarkPearl

  Today I spent a good part of my day getting to grips with the stack and nasm. After looking at my notes on nasm I think this is one area for the course I am doing they could focus more on… So here are some snippets I have put together that have helped me understand a little bit about the stack… Simplest example of the stack You will probably see examples like the following in circulation… these demonstrate the simplest use of the stack… org 0x100 bits 16 jmp main main: push 42h push 43h push 44h mov ah,2h ;set to display characters pop dx    ;get the first value int 21h   ;and display it pop dx    ;get 2nd value int 21h   ;and display it pop dx    ;get 3rd value int 21h   ;and display it int 20h The output from above code would be… DCB Decoupling code using “call” and “ret” This is great, but it oversimplifies what I want to use the stack for… I do not know if this goes against the grain of assembly programmers or not, but I want to write loosely coupled assembly code – and I want to use the stack as a mechanism for passing values into my decoupled code. In nasm we have the call and return instructions, which provides a mechanism for decoupling code, for example the following could be done… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h mov dx,41h int 21h ret ;---------------------------------------- main: call displayChar int 20h   This would output the following to the console A So, it would seem that call and ret allow us to jump to segments of our code and then return back to the calling position – a form of segmenting the code into what we would called in higher order languages “functions” or “methods”. The only issue is, in higher order languages there is a way to pass parameters into the functions and return results. Because of the primitive nature of the call and ret instructions, this does not seem to be obvious. We could of course use the registers to pass values into the subroutine and set values coming out, but the problem with this is we… Have a limited number of registers Are threading our code with tight coupling (it would be hard to migrate methods outside of their intended use in a particular program to another one) With that in mind, I turn to the stack to provide a loosely coupled way of calling subroutines… First attempt with the Stack Initially I thought this would be simple… we could use code that looks as follows to achieve what I want… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h pop dx int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h   However running this application does not give the desired result, I want an ‘A’ to be returned, and I am getting something totally different (you will to). Reading up on the call and ret instructions a discovery is made… they are pushing and popping things onto and off the stack as well… When the call instruction is executed, the current value of IP (the address of the instruction to follow) is pushed onto the stack, when ret is called, the last value on the stack is popped off into the IP register. In effect what the above code is doing is as follows with the stack… push 41h push current value of ip pop current value of ip to dx pop 41h to ip This is not what I want, I need to access the 41h that I pushed onto the stack, but the call value (which is necessary) is putting something in my way. So, what to do? Remember we have other registers we can use as well as a thing called indirect addressing… So, after some reading around, I came up with the following approach using indirect addressing… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h In essence, what I have done here is used a trick with the stack pointer… it goes as follows… Push 41 onto the stack Make the call to the function, which will push the IP register onto the stack and then jump to the displayChar label Move the value in the stack point to the bp register (sp currently points at IP register) Move the at the location of bp minus 2 bytes to dx (this is now the value 41h) display it, execute the ret instruction, which pops the ip value off the stack and goes back to the calling point This approach is still very raw, some further reading around shows that I should be pushing the value of bp onto the stack before replacing it with sp, but it is the starting thread to getting loosely coupled subroutines. Let’s see if you get what the following output would be? org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+4] int 21h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h push 42h call displayChar int 20h The output is… AB Where to from here? If by any luck some assembly programmer comes along and see this code and notices that I have made some fundamental flaw in my logic… I would like to know, so please leave a comment… appreciate any feedback!

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• NDepend 4 – First Steps

  - by Ricardo Peres

  Introduction Thanks to Patrick Smacchia I had the chance to test NDepend 4. I can only say: awesome! This will be the first of a series of posts on NDepend, where I will talk about my discoveries. Keep in mind that I am just starting to use it, so more experienced users may find these too basic, I just hope I don’t say anything foolish! I must say that I am in no way affiliated with NDepend and I never actually met Patrick. Installation No installation program – a curious decision, I’m not against it -, just unzip the files to a folder and run the executable. It will optionally register itself with Visual Studio 2008, 2010 and 11 as well as RedGate’s Reflector; also, it automatically looks for updates. NDepend can either be used as a stand-alone program (with or without a GUI) or from within Visual Studio or Reflector. Getting Started One thing that really pleases me is the Getting Started section of the stand-alone, with links to pages on NDepend’s web site, featuring detailed explanations, which usually include screenshots and small videos (<5 minutes). There’s also an How do I with hierarchical navigation that guides us to through the major features so that we can easily find what we want. Usage There are two basic ways to use NDepend: Analyze .NET solutions, projects or assemblies; Compare two versions of the same assembly. I have so far not used NDepend to compare assemblies, so I will first talk about the first option. After selecting a solution and some of its projects, it generates a single HTML page with an highly detailed report of the analysis it produced. This includes some metrics such as number of lines of code, IL instructions, comments, types, methods and properties, the calculation of the cyclomatic complexity, coupling and lots of others indicators, typically grouped by type, namespace and assembly. The HTML also includes some nice diagrams depicting assembly dependencies, type and method relative proportions (according to the number of IL instructions, I guess) and assembly analysis relating to abstractness and stability. Useful, I would say. Then there’s the rules; NDepend tests the target assemblies against a set of more than 120 rules, grouped in categories Code Quality, Object Oriented Design, Design, Architecture and Layering, Dead Code, Visibility, Naming Conventions, Source Files Organization and .NET Framework Usage. The full list can be configured on the application, and an explanation of each rule can be found on the web site. Rules can be validated, violated and violated in a critical manner, and the HTML will contain the violated rules, their queries – more on this later - and results. The HTML uses some nice JavaScript effects, which allow paging and sorting of tables, so its nice to use. Similar to the rules, there are some queries that display results for a number (about 200) questions grouped as Object Oriented Design, API Breaking Changes (for assembly version comparison), Code Diff Summary (also for version comparison) and Dead Code. The difference between queries and rules is that queries are not classified as passes, violated or critically violated, just present results. The queries and rules are expressed through CQLinq, which is a very powerful LINQ derivative specific to code analysis. All of the included rules and queries can be enabled or disabled and new ones can be added, with intellisense to help. Besides the HTML report file, the NDepend application can be used to explore all analysis results, compare different versions of analysis reports and to run custom queries. Comparison to Other Analysis Tools Unlike StyleCop, NDepend only works with assemblies, not source code, so you can’t expect it to be able to enforce brackets placement, for example. It is more similar to FxCop, but you don’t have the option to analyze at the IL level, that is, other that the number of IL instructions and the complexity. What’s Next In the next days I’ll continue my exploration with a real-life test case. References The NDepend web site is http://www.ndepend.com/. Patrick keeps an updated blog on http://codebetter.com/patricksmacchia/ and he regularly monitors StackOverflow for questions tagged NDepend, which you can find on http://stackoverflow.com/questions/tagged/ndepend. The default list of CQLinq rules, queries and statistics can be found at http://www.ndepend.com/DefaultRules/webframe.html. The syntax itself is described at http://www.ndepend.com/Doc_CQLinq_Syntax.aspx and its features at http://www.ndepend.com/Doc_CQLinq_Features.aspx.

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• Changing the Game: Why Oracle is in the IT Operations Management Business

  - by DanKoloski

  v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} Next week, in Orlando, is the annual Gartner IT Operations Management Summit. Oracle is a premier sponsor of this annual event, which brings together IT executives for several days of high level talks about the state of operational management of enterprise IT. This year, Sushil Kumar, VP Product Strategy and Business Development for Oracle’s Systems & Applications Management, will be presenting on the transformation in IT Operations required to support enterprise cloud computing. IT Operations transformation is an important subject, because year after year, we hear essentially the same refrain – large enterprises spend an average of two-thirds (67%!) of their IT resources (budget, energy, time, people, etc.) on running the business, with far too little left over to spend on growing and transforming the business (which is what the business actually needs and wants). In the thirtieth year of the distributed computing revolution (give or take, depending on how you count it), it’s amazing that we have still not moved the needle on the single biggest component of enterprise IT resource utilization. Oracle is in the IT Operations Management business because when management is engineered together with the technology under management, the resulting efficiency gains can be truly staggering. To put it simply – what if you could turn that 67% of IT resources spent on running the business into 50%? Or 40%? Imagine what you could do with those resources. It’s now not just possible, but happening. This seems like a simple idea, but it is a radical change from “business as usual” in enterprise IT Operations. For the last thirty years, management has been a bolted-on afterthought – we pick and deploy our technology, then figure out how to manage it. This pervasive dysfunction is a broken cycle that guarantees high ongoing operating costs and low agility. If we want to break the cycle, we need to take a more tightly-coupled approach. As a complete applications-to-disk platform provider, Oracle is engineering management together with technology across our stack and hooking that on-premise management up live to My Oracle Support. Let’s examine the results with just one piece of the Oracle stack – the Oracle Database. Oracle began this journey with the Oracle Database 9i many years ago with the introduction of low-impact instrumentation in the database kernel (“tell me what’s wrong”) and through Database 10g, 11g and 11gR2 has successively added integrated advisory (“tell me how to fix what’s wrong”) and lifecycle management and automated self-tuning (“fix it for me, and do it on an ongoing basis for all my assets”). When enterprises take advantage of this tight-coupling, the results are game-changing. Consider the following (for a full list of public references, visit this link): British Telecom improved database provisioning time 1000% (from weeks to minutes) which allows them to provide a new DBaaS service to their internal customers with no additional resources Cerner Corporation Saved $9.5 million in CapEx and OpEx AND launched a brand-new cloud business at the same time Vodafone Group plc improved response times 50% and reduced maintenance planning times 50-60% while serving 391 million registered mobile customers Or the recent Database Manageability and Productivity Cost Comparisons: Oracle Database 11g Release 2 vs. SAP Sybase ASE 15.7, Microsoft SQL Server 2008 R2 and IBM DB2 9.7 as conducted by independent analyst firm ORC. In later entries, we’ll discuss similar results across other portions of the Oracle stack and how these efficiency gains are required to achieve the agility benefits of Enterprise Cloud. Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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• Is the design notion of layers contrived?

  - by Bruce

  Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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• Hidden Features of PHP?

  - by George Mauer

  EDIT: This didn't really start as a hidden features of PHP topic, but thats what it ended up as, so go nuts. I know this sounds like a point-whoring question but let me explain where I'm coming from. Out of college I got a job at a PHP shop. I worked there for a year and a half and thought that I had learned all there was to learn about programming. Then I got a job as a one-man internal development shop at a sizable corporation where all the work was in C#. In my commitment to the position I started reading a ton of blogs and books and quickly realized how wrong I was to think I knew everything. I learned about unit testing, dependency injection and decorator patterns, the design principle of loose coupling, the composition over inheritance debate, and so on and on and on - I am still very much absorbing it all. Needless to say my programming style has changed entirely in the last year. Now I find myself picking up a php project doing some coding for a friend's start-up and I feel completely constrained as opposed to programming in C#. It really bothers me that all variables at a class scope have to be referred to by appending '$this-' . It annoys me that none of the IDEs that I've tried have very good intellisense and that my SimpleTest unit tests methods have to start with the word 'test'. It drives me crazy that dynamic typing keeps me from specifying implicitly which parameter type a method expects, and that you have to write a switch statement to do method overloads. I can't stand that you can't have nested namespaces and have to use the :: operator to call the base class's constructor. Now I have no intention of starting a PHP vs C# debate, rather what I mean to say is that I'm sure there are some PHP features that I either don't know about or know about yet fail to use properly. I am set in my C# universe and having trouble seeing outside the glass bowl. So I'm asking, what are your favorite features of PHP? What are things you can do in it that you can't or are more difficult in the .Net languages?

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• Avoiding circular project/assembly references in Visual Studio with statically typed dependency conf

  - by svnpttrssn

  First, I want to say that I am not interested in debating about any non-helpful "answers" to my question, with suggestions to putting everything in one assembly, i.e. there is no need for anyone to provide webpages such as the page titled with "Separate Assemblies != Loose Coupling". Now, my question is if it somehow (maybe with some Visual Studio configuration to allow for circular project dependencies?) is possible to use one project/assembly (I am here calling it the "ServiceLocator" assembly) for retrieving concrete implementation classes, (e.g. with StructureMap) which can be referred to from other projects, while it of course is also necessary for the the ServiceLocator itself to refer to other projects with the interfaces and the implementations ? Visual Studio project example, illustrating the kind of dependency structure I am talking about: http://img10.imageshack.us/img10/8838/testingdependencyinject.png Please note in the above picture, the problem is how to let the classes in "ApplicationLayerServiceImplementations" retrieve and instantiate classes that implement the interfaces in "DomainLayerServiceInterfaces". The goal is here to not refer directly to the classes in "DomainLayerServiceImplementations", but rather to try using the project "ServiceLocator" to retrieve such classes, but then the circular dependency problem occurrs... For example, a "UserInterfaceLayer" project/assembly might contain this kind of code: ContainerBootstrapper.BootstrapStructureMap(); // located in "ServiceLocator" project/assembly MyDomainLayerInterface myDomainLayerInterface = ObjectFactory.GetInstance<MyDomainLayerInterface>(); // refering to project/assembly "DomainLayerServiceInterfaces" myDomainLayerInterface.MyDomainLayerMethod(); MyApplicationLayerInterface myApplicationLayerInterface = ObjectFactory.GetInstance<MyApplicationLayerInterface>(); // refering to project/assembly "ApplicationLayerServiceInterfaces" myApplicationLayerInterface.MyApplicationLayerMethod(); The above code do not refer to the implementation projects/assemblies ApplicationLayerServiceImplementations and DomainLayerServiceImplementations, which contain this kind of code: public class MyApplicationLayerImplementation : MyApplicationLayerInterface and public class MyDomainLayerImplementation : MyDomainLayerInterface The "ServiceLocator" project/assembly might contain this code: using ApplicationLayerServiceImplementations; using ApplicationLayerServiceInterfaces; using DomainLayerServiceImplementations; using DomainLayerServiceInterfaces; using StructureMap; namespace ServiceLocator { public static class ContainerBootstrapper { public static void BootstrapStructureMap() { ObjectFactory.Initialize(x => { // The two interfaces and the two implementations below are located in four different Visual Studio projects x.ForRequestedType<MyDomainLayerInterface>().TheDefaultIsConcreteType<MyDomainLayerImplementation>(); x.ForRequestedType<MyApplicationLayerInterface>().TheDefaultIsConcreteType<MyApplicationLayerImplementation>(); }); } } } So far, no problem, but the problem occurs when I want to let the class "MyApplicationLayerImplementation" in the project/assembly "ApplicationLayerServiceImplementations" use the "ServiceLocator" project/assembly for retrieving an implementation of "MyDomainLayerInterface". When I try to do that, i.e. add a reference from "MyApplicationLayerImplementation" to "ServiceLocator", then Visual Studio complains about circular dependencies between projects. Is there any nice solution to this problem, which does not imply using refactoring-unfriendly string based xml-configuration which breaks whenever an interface or class or its namespace is renamed ? / Sven

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• Recommendations for a C++ polymorphic, seekable, binary I/O interface

  - by Trevor Robinson

  I've been using std::istream and ostream as a polymorphic interface for random-access binary I/O in C++, but it seems suboptimal in numerous ways: 64-bit seeks are non-portable and error-prone due to streampos/streamoff limitations; currently using boost/iostreams/positioning.hpp as a workaround, but it requires vigilance Missing operations such as truncating or extending a file (ala POSIX ftruncate) Inconsistency between concrete implementations; e.g. stringstream has independent get/put positions whereas filestream does not Inconsistency between platform implementations; e.g. behavior of seeking pass the end of a file or usage of failbit/badbit on errors Don't need all the formatting facilities of stream or possibly even the buffering of streambuf streambuf error reporting (i.e. exceptions vs. returning an error indicator) is supposedly implementation-dependent in practice I like the simplified interface provided by the Boost.Iostreams Device concept, but it's provided as function templates rather than a polymorphic class. (There is a device class, but it's not polymorphic and is just an implementation helper class not necessarily used by the supplied device implementations.) I'm primarily using large disk files, but I really want polymorphism so I can easily substitute alternate implementations (e.g. use stringstream instead of fstream for unit tests) without all the complexity and compile-time coupling of deep template instantiation. Does anyone have any recommendations of a standard approach to this? It seems like a common situation, so I don't want to invent my own interfaces unnecessarily. As an example, something like java.nio.FileChannel seems ideal. My best solution so far is to put a thin polymorphic layer on top of Boost.Iostreams devices. For example: class my_istream { public: virtual std::streampos seek(stream_offset off, std::ios_base::seekdir way) = 0; virtual std::streamsize read(char* s, std::streamsize n) = 0; virtual void close() = 0; }; template <class T> class boost_istream : public my_istream { public: boost_istream(const T& device) : m_device(device) { } virtual std::streampos seek(stream_offset off, std::ios_base::seekdir way) { return boost::iostreams::seek(m_device, off, way); } virtual std::streamsize read(char* s, std::streamsize n) { return boost::iostreams::read(m_device, s, n); } virtual void close() { boost::iostreams::close(m_device); } private: T m_device; };

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• using a Singleton to pass credentials in a multi-tenant application a code smell?

  - by Hans Gruber

  Currently working on a multi-tenant application that employs Shared DB/Shared Schema approach. IOW, we enforce tenant data segregation by defining a TenantID column on all tables. By convention, all SQL reads/writes must include a Where TenantID = '?' clause. Not an ideal solution, but hindsight is 20/20. Anyway, since virtually every page/workflow in our app must display tenant specific data, I made the (poor) decision at the project's outset to employ a Singleton to encapsulate the current user credentials (i.e. TenantID and UserID). My thinking at the time was that I didn't want to add a TenantID parameter to each and every method signature in my Data layer. Here's what the basic pseudo-code looks like: public class UserIdentity { public UserIdentity(int tenantID, int userID) { TenantID = tenantID; UserID = userID; } public int TenantID { get; private set; } public int UserID { get; private set; } } public class AuthenticationModule : IHttpModule { public void Init(HttpApplication context) { context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest); } private void context_AuthenticateRequest(object sender, EventArgs e) { var userIdentity = _authenticationService.AuthenticateUser(sender); if (userIdentity == null) { //authentication failed, so redirect to login page, etc } else { //put the userIdentity into the HttpContext object so that //its only valid for the lifetime of a single request HttpContext.Current.Items["UserIdentity"] = userIdentity; } } } public static class CurrentUser { public static UserIdentity Instance { get { return HttpContext.Current.Items["UserIdentity"]; } } } public class WidgetRepository: IWidgetRepository{ public IEnumerable<Widget> ListWidgets(){ var tenantId = CurrentUser.Instance.TenantID; //call sproc with tenantId parameter } } As you can see, there are several code smells here. This is a singleton, so it's already not unit test friendly. On top of that you have a very tight-coupling between CurrentUser and the HttpContext object. By extension, this also means that I have a reference to System.Web in my Data layer (shudder). I want to pay down some technical debt this sprint by getting rid of this singleton for the reasons mentioned above. I have a few thoughts on what an better implementation might be, but if anyone has any guidance or lessons learned they could share, I would be much obliged.

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• Javascript self contained sandbox events and client side stack

  - by amnon

  I'm in the process of moving a JSF heavy web application to a REST and mainly JS module application . I've watched "scalable javascript application architecture" by Nicholas Zakas on yui theater (excellent video) and implemented much of the talk with good success but i have some questions : I found the lecture a little confusing in regards to the relationship between modules and sandboxes , on one had to my understanding modules should not be effected by something happening outside of their sandbox and this is why they publish events via the sandbox (and not via the core as they do access the core for hiding base libary) but each module in the application gets a new sandbox ? , shouldn't the sandbox limit events to the modoules using it ? or should events be published cross page ? e.g. : if i have two editable tables but i want to contain each one in a different sandbox and it's events effect only the modules inside that sandbox something like messabe box per table which is a different module/widget how can i do that with sandbox per module , ofcourse i can prefix the events with the moduleid but that creates coupling that i want to avoid ... and i don't want to package modules toghter as one module per combination as i already have 6-7 modules ? while i can hide the base library for small things like id selector etc.. i would still like to use the base library for module dependencies and resource loading and use something like yui loader or dojo.require so in fact i'm hiding the base library but the modules themself are defined and loaded by the base library ... seems a little strange to me libraries don't return simple js objects but usualy wrap them e.g. : u can do something like $$('.classname').each(.. which cleans the code alot , it makes no sense to wrap the base and then in the module create a dependency for the base library by executing .each but not using those features makes a lot of code written which can be left out ... and implemnting that functionality is very bug prone does anyonen have any experience with building a front side stack of this order ? how easy is it to change a base library and/or have modules from different libraries , using yui datatable but doing form validation with dojo ... ? some what of a combination of 2+4 if u choose to do something like i said and load dojo form validation widgets for inputs via yui loader would that mean dojocore is a module and the form module is dependant on it ? Thanks .

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• NSNotifications vs delegate for multiple instances of same protocol

  - by Brent Traut

  I could use some architectural advice. I've run into the following problem a few times now and I've never found a truly elegant way to solve it. The issue, described at the highest level possible:I have a parent class that would like to act as the delegate for multiple children (all using the same protocol), but when the children call methods on the parent, the parent no longer knows which child is making the call. I would like to use loose coupling (delegates/protocols or notifications) rather than direct calls. I don't need multiple handlers, so notifications seem like they might be overkill. To illustrate the problem, let me try a super-simplified example: I start with a parent view controller (and corresponding view). I create three child views and insert each of them into the parent view. I would like the parent view controller to be notified whenever the user touches one of the children. There are a few options to notify the parent: Define a protocol. The parent implements the protocol and sets itself as the delegate to each of the children. When the user touches a child view, its view controller calls its delegate (the parent). In this case, the parent is notified that a view is touched, but it doesn't know which one. Not good enough. Same as #1, but define the methods in the protocol to also pass some sort of identifier. When the child tells its delegate that it was touched, it also passes a pointer to itself. This way, the parent know exactly which view was touched. It just seems really strange for an object to pass a reference to itself. Use NSNotifications. The parent defines a separate method for each of the three children and then subscribes to the "viewWasTouched" notification for each of the three children as the notification sender. The children don't need to attach themselves to the user dictionary, but they do need to send the notification with a pointer to themselves as the scope. Same as #4, but rather than using separate methods, the parent could just use one with a switch case or other branching along with the notification's sender to determine which path to take. Create multiple man-in-the-middle classes that act as the delegates to the child views and then call methods on the parent either with a pointer to the child or with some other differentiating factor. This approach doesn't seem scalable. Are any of these approaches considered best practice? I can't say for sure, but it feels like I'm missing something more obvious/elegant.

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• Loosely coupled implicit conversion

  - by ltjax

  Implicit conversion can be really useful when types are semantically equivalent. For example, imagine two libraries that implement a type identically, but in different namespaces. Or just a type that is mostly identical, except for some semantic-sugar here and there. Now you cannot pass one type into a function (in one of those libraries) that was designed to use the other, unless that function is a template. If it's not, you have to somehow convert one type into the other. This should be trivial (or otherwise the types are not so identical after-all!) but calling the conversion explicitly bloats your code with mostly meaningless function-calls. While such conversion functions might actually copy some values around, they essentially do nothing from a high-level "programmers" point-of-view. Implicit conversion constructors and operators could obviously help, but they introduce coupling, so that one of those types has to know about the other. Usually, at least when dealing with libraries, that is not the case, because the presence of one of those types makes the other one redundant. Also, you cannot always change libraries. Now I see two options on how to make implicit conversion work in user-code: The first would be to provide a proxy-type, that implements conversion-operators and conversion-constructors (and assignments) for all the involved types, and always use that. The second requires a minimal change to the libraries, but allows great flexibility: Add a conversion-constructor for each involved type that can be externally optionally enabled. For example, for a type A add a constructor: template <class T> A( const T& src, typename boost::enable_if<conversion_enabled<T,A>>::type* ignore=0 ) { *this = convert(src); } and a template template <class X, class Y> struct conversion_enabled : public boost::mpl::false_ {}; that disables the implicit conversion by default. Then to enable conversion between two types, specialize the template: template <> struct conversion_enabled<OtherA, A> : public boost::mpl::true_ {}; and implement a convert function that can be found through ADL. I would personally prefer to use the second variant, unless there are strong arguments against it. Now to the actual question(s): What's the preferred way to associate types for implicit conversion? Are my suggestions good ideas? Are there any downsides to either approach? Is allowing conversions like that dangerous? Should library implementers in-general supply the second method when it's likely that their type will be replicated in software they are most likely beeing used with (I'm thinking of 3d-rendering middle-ware here, where most of those packages implement a 3D vector).

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• how to avoid clutch billiard balls?

  - by Nait87

  I'm working on the simple behaviour of billiard balls in a collision with each other. All works normal, but there was a problem when facing a few easy balls is the effect of coupling balls and they're cool with each other. Tell me how to prevent this. bool MGBilliard::CollisingBall(CCPoint curr_point, CCPoint next_point) { float dx = next_point.x - (curr_point.x + dvdt.x); float dy = next_point.y - (curr_point.y - dvdt.y); float d = dx*dx+dy*dy; return d <= BALL_RADIUS * BALL_RADIUS; } double MGBilliard::angleCollisionBalls(Ball* current, Ball* next) { double na; double dx = fabs(next->location.x - current->location.x); double dy = fabs(next->location.y - current->location.y); na = atan(fabs(dy/dx)); if(atan(fabs(current->location.y/current->location.x)) < atan(fabs(next->location.y/next->location.x))) na = current->angle - na; else if(atan(fabs(current->location.y/current->location.x)) > atan(fabs(next->location.y/next->location.x))) na = current->angle + na; return na; } for(unsigned int i = 0;i<BALL_COUNT;++i) { if(vBalls[i]->speed > 0){ vBalls[i]->speed += vBalls[i]->acceleration; float dsdt = vBalls[i]->speed*dt; dvdt.x = dsdt*cos(vBalls[i]->angle); dvdt.y = dsdt*sin(vBalls[i]->angle); vBalls[i]->location.x += dvdt.x; vBalls[i]->location.y += dvdt.y; for(unsigned int j = 1; j < BALL_COUNT; ++j) { if(i == j) continue; if(CollisingBall(vBalls[i]->spriteBall->getPosition(),vBalls[j]->spriteBall->getPosition())) { vBalls[j]->speed = 600; double angle; angle = angleCollisionBalls(vBalls[i],vBalls[j]); vBalls[i]->angle = (float)-angle; vBalls[j]->angle = (float)angle; } } } }

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• Dependency Injection in ASP.NET MVC NerdDinner App using Ninject

  - by shiju

  In this post, I am applying Dependency Injection to the NerdDinner application using Ninject. The controllers of NerdDinner application have Dependency Injection enabled constructors. So we can apply Dependency Injection through constructor without change any existing code. A Dependency Injection framework injects the dependencies into a class when the dependencies are needed. Dependency Injection enables looser coupling between classes and their dependencies and provides better testability of an application and it removes the need for clients to know about their dependencies and how to create them. If you are not familiar with Dependency Injection and Inversion of Control (IoC), read Martin Fowler’s article Inversion of Control Containers and the Dependency Injection pattern. The Open Source Project NerDinner is a great resource for learning ASP.NET MVC.  A free eBook provides an end-to-end walkthrough of building NerdDinner.com application. The free eBook and the Open Source Nerddinner application are extremely useful if anyone is trying to lean ASP.NET MVC. The first release of  Nerddinner was as a sample for the first chapter of Professional ASP.NET MVC 1.0. Currently the application is updating to ASP.NET MVC 2 and you can get the latest source from the source code tab of Nerddinner at http://nerddinner.codeplex.com/SourceControl/list/changesets. I have taken the latest ASP.NET MVC 2 source code of the application and applied  Dependency Injection using Ninject and Ninject extension Ninject.Web.Mvc.Ninject &  Ninject.Web.MvcNinject is available at http://github.com/enkari/ninject and Ninject.Web.Mvc is available at http://github.com/enkari/ninject.web.mvcNinject is a lightweight and a great dependency injection framework for .NET.  Ninject is a great choice of dependency injection framework when building ASP.NET MVC applications. Ninject.Web.Mvc is an extension for ninject which providing integration with ASP.NET MVC.Controller constructors and dependencies of NerdDinner application Listing 1 – Constructor of DinnersController  public DinnersController(IDinnerRepository repository) {     dinnerRepository = repository; }  Listing 2 – Constrcutor of AccountControllerpublic AccountController(IFormsAuthentication formsAuth, IMembershipService service) {     FormsAuth = formsAuth ?? new FormsAuthenticationService();     MembershipService = service ?? new AccountMembershipService(); }  Listing 3 – Constructor of AccountMembership – Concrete class of IMembershipService public AccountMembershipService(MembershipProvider provider) {     _provider = provider ?? Membership.Provider; }    Dependencies of NerdDinnerDinnersController, RSVPController SearchController and ServicesController have a dependency with IDinnerRepositiry. The concrete implementation of IDinnerRepositiry is DinnerRepositiry. AccountController has dependencies with IFormsAuthentication and IMembershipService. The concrete implementation of IFormsAuthentication is FormsAuthenticationService and the concrete implementation of IMembershipService is AccountMembershipService. The AccountMembershipService has a dependency with ASP.NET Membership Provider. Dependency Injection in NerdDinner using NinjectThe below steps will configure Ninject to apply controller injection in NerdDinner application.Step 1 – Add reference for NinjectOpen the  NerdDinner application and add  reference to Ninject.dll and Ninject.Web.Mvc.dll. Both are available from http://github.com/enkari/ninject and http://github.com/enkari/ninject.web.mvcStep 2 – Extend HttpApplication with NinjectHttpApplication Ninject.Web.Mvc extension allows integration between the Ninject and ASP.NET MVC. For this, you have to extend your HttpApplication with NinjectHttpApplication. Open the Global.asax.cs and inherit your MVC application from  NinjectHttpApplication instead of HttpApplication.   public class MvcApplication : NinjectHttpApplication Then the Application_Start method should be replace with OnApplicationStarted method. Inside the OnApplicationStarted method, call the RegisterAllControllersIn() method.   protected override void OnApplicationStarted() {     AreaRegistration.RegisterAllAreas();     RegisterRoutes(RouteTable.Routes);     ViewEngines.Engines.Clear();     ViewEngines.Engines.Add(new MobileCapableWebFormViewEngine());     RegisterAllControllersIn(Assembly.GetExecutingAssembly()); }  The RegisterAllControllersIn method will enables to activating all controllers through Ninject in the assembly you have supplied .We are passing the current assembly as parameter for RegisterAllControllersIn() method. Now we can expose dependencies of controller constructors and properties to request injectionsStep 3 – Create Ninject ModulesWe can configure your dependency injection mapping information using Ninject Modules.Modules just need to implement the INinjectModule interface, but most should extend the NinjectModule class for simplicity. internal class ServiceModule : NinjectModule {     public override void Load()     {                    Bind<IFormsAuthentication>().To<FormsAuthenticationService>();         Bind<IMembershipService>().To<AccountMembershipService>();                  Bind<MembershipProvider>().ToConstant(Membership.Provider);         Bind<IDinnerRepository>().To<DinnerRepository>();     } } The above Binding inforamtion specified in the Load method tells the Ninject container that, to inject instance of DinnerRepositiry when there is a request for IDinnerRepositiry and  inject instance of FormsAuthenticationService when there is a request for IFormsAuthentication and inject instance of AccountMembershipService when there is a request for IMembershipService. The AccountMembershipService class has a dependency with ASP.NET Membership provider. So we configure that inject the instance of Membership Provider. When configuring the binding information, you can specify the object scope in you application.There are four built-in scopes available in Ninject:Transient  -  A new instance of the type will be created each time one is requested. (This is the default scope). Binding method is .InTransientScope()   Singleton - Only a single instance of the type will be created, and the same instance will be returned for each subsequent request. Binding method is .InSingletonScope()Thread -  One instance of the type will be created per thread. Binding method is .InThreadScope() Request -  One instance of the type will be created per web request, and will be destroyed when the request ends. Binding method is .InRequestScope() Step 4 – Configure the Ninject KernelOnce you create NinjectModule, you load them into a container called the kernel. To request an instance of a type from Ninject, you call the Get() extension method. We can configure the kernel, through the CreateKernel method in the Global.asax.cs. protected override IKernel CreateKernel() {     var modules = new INinjectModule[]     {         new ServiceModule()     };       return new StandardKernel(modules); } Here we are loading the Ninject Module (ServiceModule class created in the step 3)  onto the container called the kernel for performing dependency injection.Source CodeYou can download the source code from http://nerddinneraddons.codeplex.com. I just put the modified source code onto CodePlex repository. The repository will update with more add-ons for the NerdDinner application.

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• The Incremental Architect&acute;s Napkin - #1 - It&acute;s about the money, stupid

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/05/24/the-incremental-architectacutes-napkin---1---itacutes-about-the.aspx Software development is an economic endeavor. A customer is only willing to pay for value. What makes a software valuable is required to become a trait of the software. We as software developers thus need to understand and then find a way to implement requirements. Whether or in how far a customer really can know beforehand what´s going to be valuable for him/her in the end is a topic of constant debate. Some aspects of the requirements might be less foggy than others. Sometimes the customer does not know what he/she wants. Sometimes he/she´s certain to want something - but then is not happy when that´s delivered. Nevertheless requirements exist. And developers will only be paid if they deliver value. So we better focus on doing that. Although is might sound trivial I think it´s important to state the corollary: We need to be able to trace anything we do as developers back to some requirement. You decide to use Go as the implementation language? Well, what´s the customer´s requirement this decision is linked to? You decide to use WPF as the GUI technology? What´s the customer´s requirement? You decide in favor of a layered architecture? What´s the customer´s requirement? You decide to put code in three classes instead of just one? What´s the customer´s requirement behind that? You decide to use MongoDB over MySql? What´s the customer´s requirement behind that? etc. I´m not saying any of these decisions are wrong. I´m just saying whatever you decide be clear about the requirement that´s driving your decision. You have to be able to answer the question: Why do you think will X deliver more value to the customer than the alternatives? Customers are not interested in romantic ideals of hard working, good willing, quality focused craftsmen. They don´t care how and why you work - as long as what you deliver fulfills their needs. They want to trust you to recognize this as your top priority - and then deliver. That´s all. Fundamental aspects of requirements If you´re like me you´re probably not used to such scrutinization. You want to be trusted as a professional developer - and decide quite a few things following your gut feeling. Or by relying on “established practices”. That´s ok in general and most of the time - but still… I think we should be more conscious about our decisions. Which would make us more responsible, even more professional. But without further guidance it´s hard to reason about many of the myriad decisions we´ve to make over the course of a software project. What I found helpful in this situation is structuring requirements into fundamental aspects. Instead of one large heap of requirements then there are smaller blobs. With them it´s easier to check if a decisions falls in their scope. Sure, every project has it´s very own requirements. But all of them belong to just three different major categories, I think. Any requirement either pertains to functionality, non-functional aspects or sustainability. For short I call those aspects: Functionality, because such requirements describe which transformations a software should offer. For example: A calculator software should be able to add and multiply real numbers. An auction website should enable you to set up an auction anytime or to find auctions to bid for. Quality, because such requirements describe how functionality is supposed to work, e.g. fast or secure. For example: A calculator should be able to calculate the sinus of a value much faster than you could in your head. An auction website should accept bids from millions of users. Security of Investment, because functionality and quality need not just be delivered in any way. It´s important to the customer to get them quickly - and not only today but over the course of several years. This aspect introduces time into the “requrements equation”. Security of Investments (SoI) sure is a non-functional requirement. But I think it´s important to not subsume it under the Quality (Q) aspect. That´s because SoI has quite special properties. For one, SoI for software means something completely different from what it means for hardware. If you buy hardware (a car, a hair blower) you find that a worthwhile investment, if the hardware does not change it´s functionality or quality over time. A car still running smoothly with hardly any rust spots after 10 years of daily usage would be a very secure investment. So for hardware (or material products, if you like) “unchangeability” (in the face of usage) is desirable. With software you want the contrary. Software that cannot be changed is a waste. SoI for software means “changeability”. You want to be sure that the software you buy/order today can be changed, adapted, improved over an unforseeable number of years so as fit changes in its usage environment. But that´s not the only reason why the SoI aspect is special. On top of changeability[1] (or evolvability) comes immeasurability. Evolvability cannot readily be measured by counting something. Whether the changeability is as high as the customer wants it, cannot be determined by looking at metrics like Lines of Code or Cyclomatic Complexity or Afferent Coupling. They may give a hint… but they are far, far from precise. That´s because of the nature of changeability. It´s different from performance or scalability. Also it´s because a customer cannot tell upfront, “how much” evolvability he/she wants. Whether requirements regarding Functionality (F) and Q have been met, a customer can tell you very quickly and very precisely. A calculation is missing, the calculation takes too long, the calculation time degrades with increased load, the calculation is accessible to the wrong users etc. That´s all very or at least comparatively easy to determine. But changeability… That´s a whole different thing. Nevertheless over time the customer will develop a feedling if changeability is good enough or degrading. He/she just has to check the development of the frequency of “WTF”s from developers ;-) F and Q are “timeless” requirement categories. Customers want us to deliver on them now. Just focusing on the now, though, is rarely beneficial in the long run. So SoI adds a counterweight to the requirements picture. Customers want SoI - whether they know it or not, whether they state if explicitly or not. In closing A customer´s requirements are not monolithic. They are not all made the same. Rather they fall into different categories. We as developers need to recognize these categories when confronted with some requirement - and take them into account. Only then can we make true professional decisions, i.e. conscious and responsible ones. I call this fundamental trait of software “changeability” and not “flexibility” to distinguish to whom it´s a concern. “Flexibility” to me means, software as is can easily be adapted to a change in its environment, e.g. by tweaking some config data or adding a library which gets picked up by a plug-in engine. “Flexibiltiy” thus is a matter of some user. “Changeability”, on the other hand, to me means, software can easily be changed in its structure to adapt it to new requirements. That´s a matter of the software developer. ?

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• Enhanced REST Support in Oracle Service Bus 11gR1

  - by jeff.x.davies

  In a previous entry on REST and Oracle Service Bus (see http://blogs.oracle.com/jeffdavies/2009/06/restful_services_with_oracle_s_1.html) I encoded the REST query string really as part of the relative URL. For example, consider the following URI: http://localhost:7001/SimpleREST/Products/id=1234 Now, technically there is nothing wrong with this approach. However, it is generally more common to encode the search parameters into the query string. Take a look at the following URI that shows this principle http://localhost:7001/SimpleREST/Products?id=1234 At first blush this appears to be a trivial change. However, this approach is more intuitive, especially if you are passing in multiple parameters. For example: http://localhost:7001/SimpleREST/Products?cat=electronics&subcat=television&mfg=sony The above URI is obviously used to retrieve a list of televisions made by Sony. In prior versions of OSB (before 11gR1PS3), parsing the query string of a URI was more difficult than in the current release. In 11gR1PS3 it is now much easier to parse the query strings, which in turn makes developing REST services in OSB even easier. In this blog entry, we will re-implement the REST-ful Products services using query strings for passing parameter information. Lets begin with the implementation of the Products REST service. This service is implemented in the Products.proxy file of the project. Lets begin with the overall structure of the service, as shown in the following screenshot. This is a common pattern for REST services in the Oracle Service Bus. You implement different flows for each of the HTTP verbs that you want your service to support. Lets take a look at how the GET verb is implemented. This is the path that is taken of you were to point your browser to: http://localhost:7001/SimpleREST/Products/id=1234 There is an Assign action in the request pipeline that shows how to extract a query parameter. Here is the expression that is used to extract the id parameter: $inbound/ctx:transport/ctx:request/http:query-parameters/http:parameter[@name="id"]/@value The Assign action that stores the value into an OSB variable named id. Using this type of XPath statement you can query for any variables by name, without regard to their order in the parameter list. The Log statement is there simply to provided some debugging info in the OSB server console. The response pipeline contains a Replace action that constructs the response document for our rest service. Most of the response data is static, but the ID field that is returned is set based upon the query-parameter that was passed into the REST proxy. Testing the REST service with a browser is very simple. Just point it to the URL I showed you earlier. However, the browser is really only good for testing simple GET services. The OSB Test Console provides a much more robust environment for testing REST services, no matter which HTTP verb is used. Lets see how to use the Test Console to test this GET service. Open the OSB we console (http://localhost:7001/sbconsole) and log in as the administrator. Click on the Test Console icon (the little "bug") next to the Products proxy service in the SimpleREST project. This will bring up the Test Console browser window. Unlike SOAP services, we don't need to do much work in the request document because all of our request information will be encoded into the URI of the service itself. Belore the Request Document section of the Test Console is the Transport section. Expand that section and modify the query-parameters and http-method fields as shown in the next screenshot. By default, the query-parameters field will have the tags already defined. You just need to add a tag for each parameter you want to pass into the service. For out purposes with this particular call, you'd set the quer-parameters field as follows: <tp:parameter name="id" value="1234" /> </tp:query-parameters> Now you are ready to push the Execute button to see the results of the call. That covers the process for parsing query parameters using OSB. However, what if you have an OSB proxy service that needs to consume a REST-ful service? How do you tell OSB to pass the query parameters to the external service? In the sample code you will see a 2nd proxy service called CallREST. It invokes the Products proxy service in exactly the same way it would invoke any REST service. Our CallREST proxy service is defined as a SOAP service. This help to demonstrate OSBs ability to mediate between service consumers and service providers, decreasing the level of coupling between them. If you examine the message flow for the CallREST proxy service, you'll see that it uses an Operational branch to isolate processing logic for each operation that is defined by the SOAP service. We will focus on the getProductDetail branch, that calls the Products REST service using the HTTP GET verb. Expand the getProduct pipeline and the stage node that it contains. There is a single Assign statement that simply extracts the productID from the SOA request and stores it in a local OSB variable. Nothing suprising here. The real work (and the real learning) occurs in the Route node below the pipeline. The first thing to learn is that you need to use a route node when calling REST services, not a Service Callout or a Publish action. That's because only the Routing action has access to the $oubound variable, especially when invoking a business service. The Routing action contains 3 Insert actions. The first Insert action shows how to specify the HTTP verb as a GET. The second insert action simply inserts the XML node into the request. This element does not exist in the request by default, so we need to add it manually. Now that we have the element defined in our outbound request, we can fill it with the parameters that we want to send to the REST service. In the following screenshot you can see how we define the id parameter based on the productID value we extracted earlier from the SOAP request document. That expression will look for the parameter that has the name id and extract its value. That's all there is to it. You now know how to take full advantage of the query parameter parsing capability of the Oracle Service Bus 11gR1PS2. Download the sample source code here: rest2_sbconfig.jar Ubuntu and the OSB Test Console You will get an error when you try to use the Test Console with the Oracle Service Bus, using Ubuntu (or likely a number of other Linux distros also). The error (shown below) will state that the Test Console service is not running. The fix for this problem is quite simple. Open up the WebLogic Server administrator console (usually running at http://localhost:7001/console). In the Domain Structure window on the left side of the console, select the Servers entry under the Environment heading. The select the Admin Server entry in the main window of the console. By default, you should be viewing the Configuration tabe and the General sub tab in the main window. Look for the Listen Address field. By default it is blank, which means it is listening on all interfaces. For some reason Ubuntu doesn't like this. So enter a value like localhost or the specific IP address or DNS name for your server (usually its just localhost in development envirionments). Save your changes and restart the server. Your Test Console will now work correctly.

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• Curing the Database-Application mismatch

  - by Phil Factor

  If an application requires access to a database, then you have to be able to deploy it so as to be version-compatible with the database, in phase. If you can deploy both together, then the application and database must normally be deployed at the same version in which they, together, passed integration and functional testing.  When a single database supports more than one application, then the problem gets more interesting. I’ll need to be more precise here. It is actually the application-interface definition of the database that needs to be in a compatible ‘version’.  Most databases that get into production have no separate application-interface; in other words they are ‘close-coupled’.  For this vast majority, the whole database is the application-interface, and applications are free to wander through the bowels of the database scot-free.  If you’ve spurned the perceived wisdom of application architects to have a defined application-interface within the database that is based on views and stored procedures, any version-mismatch will be as sensitive as a kitten.  A team that creates an application that makes direct access to base tables in a database will have to put a lot of energy into keeping Database and Application in sync, to say nothing of having to tackle issues such as security and audit. It is not the obvious route to development nirvana. I’ve been in countless tense meetings with application developers who initially bridle instinctively at the apparent restrictions of being ‘banned’ from the base tables or routines of a database.  There is no good technical reason for needing that sort of access that I’ve ever come across.  Everything that the application wants can be delivered via a set of views and procedures, and with far less pain for all concerned: This is the application-interface.  If more than zero developers are creating a database-driven application, then the project will benefit from the loose-coupling that an application interface brings. What is important here is that the database development role is separated from the application development role, even if it is the same developer performing both roles. The idea of an application-interface with a database is as old as I can remember. The big corporate or government databases generally supported several applications, and there was little option. When a new application wanted access to an existing corporate database, the developers, and myself as technical architect, would have to meet with hatchet-faced DBAs and production staff to work out an interface. Sure, they would talk up the effort involved for budgetary reasons, but it was routine work, because it decoupled the database from its supporting applications. We’d be given our own stored procedures. One of them, I still remember, had ninety-two parameters. All database access was encapsulated in one application-module. If you have a stable defined application-interface with the database (Yes, one for each application usually) you need to keep the external definitions of the components of this interface in version control, linked with the application source,  and carefully track and negotiate any changes between database developers and application developers.  Essentially, the application development team owns the interface definition, and the onus is on the Database developers to implement it and maintain it, in conformance.  Internally, the database can then make all sorts of changes and refactoring, as long as source control is maintained.  If the application interface passes all the comprehensive integration and functional tests for the particular version they were designed for, nothing is broken. Your performance-testing can ‘hang’ on the same interface, since databases are judged on the performance of the application, not an ‘internal’ database process. The database developers have responsibility for maintaining the application-interface, but not its definition,  as they refactor the database. This is easily tested on a daily basis since the tests are normally automated. In this setting, the deployment can proceed if the more stable application-interface, rather than the continuously-changing database, passes all tests for the version of the application. Normally, if all goes well, a database with a well-designed application interface can evolve gracefully without changing the external appearance of the interface, and this is confirmed by integration tests that check the interface, and which hopefully don’t need to be altered at all often.  If the application is rapidly changing its ‘domain model’  in the light of an increased understanding of the application domain, then it can change the interface definitions and the database developers need only implement the interface rather than refactor the underlying database.  The test team will also have to redo the functional and integration tests which are, of course ‘written to’ the definition.  The Database developers will find it easier if these tests are done before their re-wiring  job to implement the new interface. If, at the other extreme, an application receives no further development work but survives unchanged, the database can continue to change and develop to keep pace with the requirements of the other applications it supports, and needs only to take care that the application interface is never broken. Testing is easy since your automated scripts to test the interface do not need to change. The database developers will, of course, maintain their own source control for the database, and will be likely to maintain versions for all major releases. However, this will not need to be shared with the applications that the database servers. On the other hand, the definition of the application interfaces should be within the application source. Changes in it have to be subject to change-control procedures, as they will require a chain of tests. Once you allow, instead of an application-interface, an intimate relationship between application and database, we are in the realms of impedance mismatch, over and above the obvious security problems.  Part of this impedance problem is a difference in development practices. Whereas the application has to be regularly built and integrated, this isn’t necessarily the case with the database.  An RDBMS is inherently multi-user and self-integrating. If the developers work together on the database, then a subsequent integration of the database on a staging server doesn’t often bring nasty surprises. A separate database-integration process is only needed if the database is deliberately built in a way that mimics the application development process, but which hampers the normal database-development techniques.  This process is like demanding a official walking with a red flag in front of a motor car.  In order to closely coordinate databases with applications, entire databases have to be ‘versioned’, so that an application version can be matched with a database version to produce a working build without errors.  There is no natural process to ‘version’ databases.  Each development project will have to define a system for maintaining the version level. A curious paradox occurs in development when there is no formal application-interface. When the strains and cracks happen, the extra meetings, bureaucracy, and activity required to maintain accurate deployments looks to IT management like work. They see activity, and it looks good. Work means progress.  Management then smile on the design choices made. In IT, good design work doesn’t necessarily look good, and vice versa.

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• Google Analytics on Android

  - by pjv

  There is a specific and official analytics SDK for native Android apps (note that I'm not talking about webpages in apps on a phone). This library basically sends pages and events to Google Analytics and you can view your analytics in exactly the same dashboard as for websites. Since my background is apps rather than websites, and since a lot of the Google Analytics terminology seems particularly inapplicable to a native app, I need some pointers. Please discuss my remarks, provide some clarification where you think I'm off-track, and above all share good experiences! 1. Page Views Pages mostly can match different Activities (and Dialogs) being displayed. Activities can be visible behind non-full-screen Activities however, though only the top-level Activity can be interacted. This sort-off clashes with a "(page) view". You'd also want at least one page view for each visit and therefore put one page view tracker in the Application class. However this does not constitute a window or sorts. Usually an Activity will open at the same time, so the time spent on that page will have been 0. This will influence your "time spent" statistics. How are these counted anyway? Moreover, there is a loose coupling between the Activities, by means of Intents. A user can, much like on any website, step in at any Activity, although usually this then concerns resuming the application where he left off. This makes that the hierarchy of Activities usually is very flat. And since there are no url's involved. What meaning would using slashes in page titles have, such as "/Home"? All pages would appear on an equal level in the reports, so no content drilldown. Non-unique page views seem to be counted as some kind of indicator of successfulness: how often does the visitor revisit the page. When the user rotates the screen however usually an Activity resumes again, thus making it a new page view. This happens a lot. Maybe a well-thought-through placement of the call might solve this, or placing several, I'm not sure. How to deal with Page Views? 2. Events I'd say there are two sorts: A user event Something that happened, usually as an indirect consequence of the above. The latter particularly is giving me headaches. First of all, many events aren't written in code any more, but pieced logically together by means of Intents. This means that there is no place to put the analytics call. You'd either have to give up this advantage and start doing it the old-fashioned way in favor of good analytics, or, just be missing some events. Secondly, as a developer you're not so much interested in when a user clicks a button, but if the action that should have been performed really was performed and what the result was. There seems to be no clear way to get resulting data into Google Analytics (what's up with the integers? I want to put in Strings!). The same that applies to the flat pages hierarchy, also goes for the event categories. You could do "vertical" categories (topically, that is), but some code is shared "horizontally" and the tracking will be equally shared. Just as with the Intents mechanism, inheritance makes it hard for you to put the tracking in the right places at all times. And I can't really imagine "horizontal" categories. Unless you start making really small categories, such as all the items form the same menu in one category, I have a hard time grasping the concept. Finally, how do you deal with cancelling? Usually you both have an explicit cancel mechanism by ways of a button, as well as the implicit cancel when the "back"-button is pressed to leave the activity and there were no changes. The latter also applies to "saves", when the back button is pressed and there ARE changes. How are you consequently going to catch all these if not by doing all the "back"-button work yourself? How to deal with events? 3. Goals For goal types I have choice of: URL Destination, Time on Site, and Pages/Visit. Most apps don't have a funnel that leads the user to some "registration done" or "order placed" page. Apps have either already been bought (in which case you want to stimulate the user to love your app, so that he might bring on new buyers) or are paid for by in-app ads. So URL Destination is not a very important goal. Time on Site also seems troublesome. First, I have some doubt on how this would be measured. Second, I don't necessarily want my user to spend a lot of time in my already paid app, just be active and content. Equivalently, why not mention how frequent a user uses your app? Regarding Pages/Visit I already mentioned how screen orientation changes blow up the page view numbers. In an app I'd be most interested in events/visit to measure the user's involvement/activity. If he's intensively using the app then he must be loving it right? Furthermore, I also have some small funnels (that do not lead to conversion though) that I want to see streamlined. In my mind those funnels would end in events rather than page views but that seems not to be possible. I could also measure clickthroughs on in-app ads, but then I'd need to track those as Page Views rather than Events, in view of "URL Destination". What are smart goals for apps and how can you fit them on top of Analytics? 4. Optimisation Is there a smart way to manually do what "Website Optimiser" does for websites? Most importantly, how would I track different landing page designs? 5. Traffic Sources Referrals deal with installation time referrals, if you're smart enough to get them included. But perhaps I'd also want to get some data which third-party app sends users to my app to perform some actions (this app interoperability is possible via Intents). Many of the terminologies related to "Traffic Sources" seem totally meaningless and there is no possibility of connecting in AdSense. What are smart uses of this data? 6. Visitors Of the "Browser capabilities", "Network Properties" and "Mobile" tabs, many things are pointless as they have no influence on / relation with my mostly offline app that won't use flash anyway. Only if you drill down far enough, can you get to OS versions, which do matter a lot. I even forgot where you could check what exact Android devices visited. What are smart uses of this data? How can you make the relevant info more prominent? 7. Other No in-page analytics. I have to register my app as a web-url (What!?)?

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• Entity Framework 6: Alpha2 Now Available

  - by ScottGu

  The Entity Framework team recently announced the 2nd alpha release of EF6.   The alpha 2 package is available for download from NuGet. Since this is a pre-release package make sure to select “Include Prereleases” in the NuGet package manager, or execute the following from the package manager console to install it: PM> Install-Package EntityFramework -Pre This week’s alpha release includes a bunch of great improvements in the following areas: Async language support is now available for queries and updates when running on .NET 4.5. Custom conventions now provide the ability to override the default conventions that Code First uses for mapping types, properties, etc. to your database. Multi-tenant migrations allow the same database to be used by multiple contexts with full Code First Migrations support for independently evolving the model backing each context. Using Enumerable.Contains in a LINQ query is now handled much more efficiently by EF and the SQL Server provider resulting greatly improved performance. All features of EF6 (except async) are available on both .NET 4 and .NET 4.5. This includes support for enums and spatial types and the performance improvements that were previously only available when using .NET 4.5. Start-up time for many large models has been dramatically improved thanks to improved view generation performance. Below are some additional details about a few of the improvements above: Async Support .NET 4.5 introduced the Task-Based Asynchronous Pattern that uses the async and await keywords to help make writing asynchronous code easier. EF 6 now supports this pattern. This is great for ASP.NET applications as database calls made through EF can now be processed asynchronously – avoiding any blocking of worker threads. This can increase scalability on the server by allowing more requests to be processed while waiting for the database to respond. The following code shows an MVC controller that is querying a database for a list of location entities:     public class HomeController : Controller     {         LocationContext db = new LocationContext();           public async Task<ActionResult> Index()         {             var locations = await db.Locations.ToListAsync();               return View(locations);         }     } Notice above the call to the new ToListAsync method with the await keyword. When the web server reaches this code it initiates the database request, but rather than blocking while waiting for the results to come back, the thread that is processing the request returns to the thread pool, allowing ASP.NET to process another incoming request with the same thread. In other words, a thread is only consumed when there is actual processing work to do, allowing the web server to handle more concurrent requests with the same resources. A more detailed walkthrough covering async in EF is available with additional information and examples. Also a walkthrough is available showing how to use async in an ASP.NET MVC application. Custom Conventions When working with EF Code First, the default behavior is to map .NET classes to tables using a set of conventions baked into EF. For example, Code First will detect properties that end with “ID” and configure them automatically as primary keys. However, sometimes you cannot or do not want to follow those conventions and would rather provide your own. For example, maybe your primary key properties all end in “Key” instead of “Id”. Custom conventions allow the default conventions to be overridden or new conventions to be added so that Code First can map by convention using whatever rules make sense for your project. The following code demonstrates using custom conventions to set the precision of all decimals to 5. As with other Code First configuration, this code is placed in the OnModelCreating method which is overridden on your derived DbContext class:         protected override void OnModelCreating(DbModelBuilder modelBuilder)         {             modelBuilder.Properties<decimal>()                 .Configure(x => x.HasPrecision(5));           } But what if there are a couple of places where a decimal property should have a different precision? Just as with all the existing Code First conventions, this new convention can be overridden for a particular property simply by explicitly configuring that property using either the fluent API or a data annotation. A more detailed description of custom code first conventions is available here. Community Involvement I blogged a while ago about EF being released under an open source license.  Since then a number of community members have made contributions and these are included in EF6 alpha 2. Two examples of community contributions are: AlirezaHaghshenas contributed a change that increases the startup performance of EF for larger models by improving the performance of view generation. The change means that it is less often necessary to use of pre-generated views. UnaiZorrilla contributed the first community feature to EF: the ability to load all Code First configuration classes in an assembly with a single method call like the following: protected override void OnModelCreating(DbModelBuilder modelBuilder) {        modelBuilder.Configurations            .AddFromAssembly(typeof(LocationContext).Assembly); } This code will find and load all the classes that inherit from EntityTypeConfiguration<T> or ComplexTypeConfiguration<T> in the assembly where LocationContext is defined. This reduces the amount of coupling between the context and Code First configuration classes, and is also a very convenient shortcut for large models. Other upcoming features coming in EF 6 Lots of information about the development of EF6 can be found on the EF CodePlex site, including a roadmap showing the other features that are planned for EF6. One of of the nice upcoming features is connection resiliency, which will automate the process of retying database operations on transient failures common in cloud environments and with databases such as the Windows Azure SQL Database. Another often requested feature that will be included in EF6 is the ability to map stored procedures to query and update operations on entities when using Code First. Summary EF6 is the first open source release of Entity Framework being developed in CodePlex. The alpha 2 preview release of EF6 is now available on NuGet, and contains some really great features for you to try. The EF team are always looking for feedback from developers - especially on the new features such as custom Code First conventions and async support. To provide feedback you can post a comment on the EF6 alpha 2 announcement post, start a discussion or file a bug on the CodePlex site. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• Replace conditional with polymorphism refactoring or similar?

  - by Anders Svensson

  Hi, I have tried to ask a variant of this question before. I got some helpful answers, but still nothing that felt quite right to me. It seems to me this shouldn't really be that hard a nut to crack, but I'm not able to find an elegant simple solution. (Here's my previous post, but please try to look at the problem stated here as procedural code first so as not to be influenced by the earlier explanation which seemed to lead to very complicated solutions: http://stackoverflow.com/questions/2772858/design-pattern-for-cost-calculator-app ) Basically, the problem is to create a calculator for hours needed for projects that can contain a number of services. In this case "writing" and "analysis". The hours are calculated differently for the different services: writing is calculated by multiplying a "per product" hour rate with the number of products, and the more products are included in the project, the lower the hour rate is, but the total number of hours is accumulated progressively (i.e. for a medium-sized project you take both the small range pricing and then add the medium range pricing up to the number of actual products). Whereas for analysis it's much simpler, it is just a bulk rate for each size range. How would you be able to refactor this into an elegant and preferably simple object-oriented version (please note that I would never write it like this in a purely procedural manner, this is just to show the problem in another way succinctly). I have been thinking in terms of factory, strategy and decorator patterns, but can't get any to work well. (I read Head First Design Patterns a while back, and both the decorator and factory patterns described have some similarities to this problem, but I have trouble seeing them as good solutions as stated there. The decorator example seems very complicated for just adding condiments, but maybe it could work better here, I don't know. And the factory pattern example with the pizza factory...well it just seems to create such a ridiculous explosion of classes, at least in their example. I have found good use for factory patterns before, but I can't see how I could use it here without getting a really complicated set of classes) The main goal would be to only have to change in one place (loose coupling etc) if I were to add a new parameter (say another size, like XSMALL, and/or another service, like "Administration"). Here's the procedural code example: public class Conditional { private int _numberOfManuals; private string _serviceType; private const int SMALL = 2; private const int MEDIUM = 8; public int GetHours() { if (_numberOfManuals <= SMALL) { if (_serviceType == "writing") return 30 * _numberOfManuals; if (_serviceType == "analysis") return 10; } else if (_numberOfManuals <= MEDIUM) { if (_serviceType == "writing") return (SMALL * 30) + (20 * _numberOfManuals - SMALL); if (_serviceType == "analysis") return 20; } else //i.e. LARGE { if (_serviceType == "writing") return (SMALL * 30) + (20 * (MEDIUM - SMALL)) + (10 * _numberOfManuals - MEDIUM); if (_serviceType == "analysis") return 30; } return 0; //Just a default fallback for this contrived example } } All replies are appreciated! I hope someone has a really elegant solution to this problem that I actually thought from the beginning would be really simple... Regards, Anders

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