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  • Does anyone know of a good .Net VoIP library.

    - by Vaelen
    I have been searching for ages now for a good .Net based VoIP library. After having tried conaito and SIP.Net I have still haven't found anything that truly fits my needs. Basically all of these are constructed using ActiveX. Unfortunately ActiveX and WPF don't play well together. And ClickOnce Deployment doesn't register Interop COM components. I need to find a good, pure .Net managed code implementation.

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  • Do assembly strong names change when new versions of .Net are released?

    - by Ryan Michela
    I'm trying to load an assembly that was installed as part of .Net 3.5 SP1 using Assembly.Load() by referencing its strong name. This works fine on my computer right now, but is it future proof? Will the strong name of core .Net assemblies change when patches are installed or new versions of the .Net framework are released? If so, how can I load an assembly from the GAC without using it's strong name?

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  • why a .net 1.1 code gets compiled in 2.0 and throws an error?

    - by Sanjeev
    Hi I have a web projects which is build in VS2003/1.1 framework and deployed in a webserver with IIS setting specified to 1.1 framework.lets say project X I also have another web project which is build with VS2008/2.0. IIS setting - ASP version 2.0 is selected and all pages are assigned to run with 2.0* dlls. Lets say project Y Now the problem seem to be when I hit project x, sometimes it throws errors like "error BC30456: 'Initialize Culture' is not a member of 'ASP.**" During troubleshooting this issue, I browsed through 2.0 Temporary ASP.Net files "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\" and found temp files generated for project X. (HUH?) How/why 1.1 project gets compiled in 2.0 only when it errors out.( or we could put it this way that it errors out every time it gets compiled in 2.0 which it is not supposed to) I'm confused as to why this is happening when project X has nothing to do with .net 2.0.

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  • can wsdl generated from java web service using apache cxf be similarly implemented as a .net web ser

    - by user335092
    Hi, i have a web service implemented in java using apache cxf and spring. But the requirement is the same i need that service to be implemented in .net and use that service with my java project web service client..... the package structure of the interface and its implementation should be simulated in .net..... i am novoice to .net and donno how it can be done... any help is appreciated..........

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  • Can I use a attribute to make .net impersonate another user?

    - by Rising Star
    I am familiar with impersonating an account in .net by using: dim myIdentity as WindowsIdentity = someIdentity using ctx as WindowsImpersonationContext = myIdentity.Impersonate() doStuff() end using Is it possible to define a .net attribute so that I could write something like: < runAsUser(someIdentity) public sub doStuff() and then have the .net framework always impersonate when running the method doStuff()?

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  • How to disable current page links in ASP.NET MVC?

    - by rem
    I'm investigating ASP.NET MVC now and noticed that in ASP.NET MVC application, which is created by Visual Studio by default, links "Home" and "About" are staying active when the user is on "Home" and "About" page correspondingly, and after clicking on the current page link page is reloading itself. What is the correct approach to disable link which points to the page, a user is already on? How to do it without violating ASP.NET MVC approach?

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  • .NET security mechanism to restrict access between two Types in the same Website project?

    - by jdk
    Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project (Note: Not a Web Application). Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. I'm unsure. I don't really care whether the solution actually hides classes from each other or just makes them inaccessible, etc. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ... Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the ASP.NET Website project.

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  • Know of any open source projects written in C#, that don’t use any other .Net related technologies

    - by AspOnMyNet
    Do you know of any open source code that would go beyond the basic exercises (aka demonstrations of how particular C# construct works), thus a C# code that would have some real world value? I did read similar threads ( http://stackoverflow.com/questions/1391909/as-a-net-beginner-what-should-i-learn-and-where-can-i-find-open-source-projects ) and the sites suggested (like http://www.codeplex.com and http://sourceforge.net), but all the apps I’ve found there are built using C# in conjunction with other technologies ( such as WinForms, Asp.Net, WCF, WPF, F#,Javascript ), while at the moment all I know is C#, a bit of Html and a bit of Ado.Net. I do plan to learn these technologies also, but that could take months while I’d like to create some useful C# apps right now. thanx

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  • Some VS 2010 RC Updates (including patches for Intellisense and Web Designer fixes)

    - by ScottGu
    [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu] We are continuing to make progress on shipping Visual Studio 2010.  I’d like to say a big thank you to everyone who has downloaded and tried out the VS 2010 Release Candidate, and especially to those who have sent us feedback or reported issues with it. This data has been invaluable in helping us find and fix remaining bugs before we ship the final release. Last month I blogged about a patch we released for the VS 2010 RC that fixed a bad intellisense crash issue.  This past week we released two additional patches that you can download and apply to the VS 2010 RC to immediately fix two other common issues we’ve seen people run into: Patch that fixes crashes with Tooltip invocation and when hovering over identifiers The Visual Studio team recently released a second patch that fixes some crashes we’ve seen when tooltips are displayed – most commonly when hovering over an identifier to view a QuickInfo tooltip. You can learn more about this issue from this blog post, and download and apply the patch here. Patch that fixes issues with the Web Forms designer not correctly adding controls to the auto-generated designer files The Visual Web Developer team recently released a patch that fixes issues where web controls are not correctly added to the .designer.cs file associated with the .aspx file – which means they can’t be programmed against in the code-behind file.  This issue is most commonly described as “controls are not being recognized in the code-behind” or “editing existing .aspx files regenerates the .aspx.designer.(vb or cs) file and controls are now missing” or “I can’t embed controls within the Ajax Control Toolkit TabContainer or the <asp:createuserwizard> control”. You can learn more about the issue here, and download the patch that fixes it here. Common Cause of Intellisense and IDE sluggishness on Windows XP, Vista, Win Server 2003/2008 systems Over the last few months we’ve occasionally seen reports of people seeing tremendous slowness when typing and using intellisense within VS 2010 despite running on decent machines.  It took us awhile to track down the cause – but we have found that the common culprit seems to be that these machines don’t have the latest versions of the UIA (Windows Automation) component installed. UIA 3 ships with Windows 7, and is a recommended Windows Update patch on XP and Vista (which is why we didn’t see the problem in our tests – since our machines are patched with all recommended updates).  Many systems (especially on XP) don’t automatically install recommended updates, though, and are running with older versions of UIA. This can cause significant performance slow-downs within the VS 2010 editor when large lists are displayed (for example: with intellisense). If you are running on Windows XP, Vista, or Windows Server 2003 or 2008 and are seeing any performance issues with the editor or IDE, please install the free UIA 3 update that can be downloaded from this page.  If you scroll down the page you’ll find direct links to versions for each OS. Note that we are making improvements to the final release of VS 2010 so that we don’t have big perf issues when UIA 3 isn’t installed – and we are also adding a message within the IDE that will warn you if you don’t have UIA 3 installed and accessibility is activated. Improved Text Rendering with WPF 4 and VS 2010 We recently made some nice changes to WPF 4 which improve the text clarity and text crispness over what was in the VS 2010/.NET 4 Release Candidate.  In particular these changes improve scenarios where you have a dark background with light text. You can learn more about these improvements in this WPF Team blog post.  These changes will be in the final release of VS 2010 and .NET 4. Hope this helps, Scott

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  • Things to install on a new machine – revisited

    - by RoyOsherove
    as I prepare to get a new dev machine at work, I write the things I am going to install on it, before writing the first line of code on that machine: Control Freak Tools: Everything Search Engine – a free and amazingly fast search engine for files all over your machine. (just file names, not inside files). This is so fast I use it almost as a replacement for my start menu, but it’s also great for finding those files that get hidden and tucked away in dark places on my system. Ever had a situation where you needed to see exactly how many copies of X.dll were hiding on your machine and where? this tool is perfect for that. Google Chrome. It’s just fast. very fast. and Firefox has become the IE of alternative browsers in terms of speed and memory. Don’t even get me started on IE. TweetDeck – get a complete view of what’s up on twitter Total Commander – my still favorite file manager, over five years now. KatMouse – will scroll any window your hovering on, even if it’s not an active window, when you use scroll the wheel on it. PowerIso or Daemon Tools – for loading up ISO images of discs LogMeIn Ignition – quick access to your LogMeIn computers for online Backup: JungleDisk or BackBlaze KeePass – save important passwords MS Security Essentials – free anti virus that’s quoest and doesn’t make a mess of your system. for home: uTorrent – a torrent client that can read rss feeds (like the ones from ezrss.it ) Camtasia Studio and SnagIt – for recording and capturing the screen, and then adding cool effects on top. Foxit PDF Reader – much faster that adove reader. Toddler Keys (for home) – for when your baby wants to play with your keyboard. Live Writer – for writing blog posts for Lenovo ThinkPads – Lenovo System Update – if you have a “custom” system instead of the one that came built in, this will keep all your lenovo drivers up to date. FileZilla – for FTP stuff All the utils from sysinternals, (or try the live-links) especially: AutoRuns for deciding what’s really going to load at startup, procmon to see what’s really going on with processes in your system   Developer stuff: Reflector. Pure magic. Time saver. See source code of any compiled assembly. Resharper. Great for productivity and navigation across your source code FinalBuilder – a commercial build automation tool. Love it. much better than any xml based time hog out there. TeamCity – a great visual and friendly server to manage continuous integration. powerful features. Test Lint – a free addin for vs 2010 I helped create, that checks your unit tests for possible problems and hints you about it. TestDriven.NET – a great test runner for vs 2008 and 2010 with some powerful features. VisualSVN – a commercial tool if you use subversion. very reliable addin for vs 2008 and 2010 Beyond Compare – a powerful file and directory comparison tool. I love the fact that you can right click in windows exporer on any file and select “select left side to compare”, then right click on another file and select “compare with left side”. Great usability thought! PostSharp 2.0 – for addind system wide concepts into your code (tracing, exception management). Goes great hand in hand with.. SmartInspect – a powerful framework and viewer for tracing for your application. lots of hidden features. Crypto Obfuscator – a relatively new obfuscation tool for .NET that seems to do the job very well. Crypto Licensing – from the same company –finally a licensing solution that seems to really fit what I needed. And it works. Fiddler 2 – great for debugging and tracing http traffic to and from your app. Debugging Tools for Windows and DebugDiag  - great for debugging scenarios. still wanting more? I think this should keep you busy for a while.   Regulator and Regulazy – for testing and generating regular expressions Notepad 2 – for quick editing and viewing with syntax highlighting

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  • MongoDB usage best practices

    - by andresv
    The project I'm working on uses MongoDB for some stuff so I'm creating some documents to help developers speedup the learning curve and also avoid mistakes and help them write clean & reliable code. This is my first version of it, so I'm pretty sure I will be adding more stuff to it, so stay tuned! C# Official driver notes The 10gen official MongoDB driver should always be referenced in projects by using NUGET. Do not manually download and reference assemblies in any project. C# driver quickstart guide: http://www.mongodb.org/display/DOCS/CSharp+Driver+Quickstart Reference links C# Language Center: http://www.mongodb.org/display/DOCS/CSharp+Language+Center MongoDB Server Documentation: http://www.mongodb.org/display/DOCS/Home MongoDB Server Downloads: http://www.mongodb.org/downloads MongoDB client drivers download: http://www.mongodb.org/display/DOCS/Drivers MongoDB Community content: http://www.mongodb.org/display/DOCS/CSharp+Community+Projects Tutorials Tutorial MongoDB con ASP.NET MVC - Ejemplo Práctico (Spanish):http://geeks.ms/blogs/gperez/archive/2011/12/02/tutorial-mongodb-con-asp-net-mvc-ejemplo-pr-225-ctico.aspx MongoDB and C#:http://www.codeproject.com/Articles/87757/MongoDB-and-C C# driver LINQ tutorial:http://www.mongodb.org/display/DOCS/CSharp+Driver+LINQ+Tutorial C# driver reference: http://www.mongodb.org/display/DOCS/CSharp+Driver+Tutorial Safe Mode Connection The C# driver supports two connection modes: safe and unsafe. Safe connection mode (only applies to methods that modify data in a database like Inserts, Deletes and Updates. While the current driver defaults to unsafe mode (safeMode == false) it's recommended to always enable safe mode, and force unsafe mode on specific things we know aren't critical. When safe mode is enabled, the driver internal code calls the MongoDB "getLastError" function to ensure the last operation is completed before returning control the the caller. For more information on using safe mode and their implicancies on performance and data reliability see: http://www.mongodb.org/display/DOCS/getLastError+Command If safe mode is not enabled, all data modification calls to the database are executed asynchronously (fire & forget) without waiting for the result of the operation. This mode could be useful for creating / updating non-critical data like performance counters, usage logging and so on. It's important to know that not using safe mode implies that data loss can occur without any notification to the caller. As with any wait operation, enabling safe mode also implies dealing with timeouts. For more information about C# driver safe mode configuration see: http://www.mongodb.org/display/DOCS/CSharp+getLastError+and+SafeMode The safe mode configuration can be specified at different levels: Connection string: mongodb://hostname/?safe=true Database: when obtaining a database instance using the server.GetDatabase(name, safeMode) method Collection: when obtaining a collection instance using the database.GetCollection(name, safeMode) method Operation: for example, when executing the collection.Insert(document, safeMode) method Some useful SafeMode article: http://stackoverflow.com/questions/4604868/mongodb-c-sharp-safemode-official-driver Exception Handling The driver ensures that an exception will be thrown in case of something going wrong, in case of using safe mode (as said above, when not using safe mode no exception will be thrown no matter what the outcome of the operation is). As explained here https://groups.google.com/forum/?fromgroups#!topic/mongodb-user/mS6jIq5FUiM there is no need to check for any returned value from a driver method inserting data. With updates the situation is similar to any other relational database: if an update command doesn't affect any records, the call will suceed anyway (no exception thrown) and you manually have to check for something like "records affected". For MongoDB, an Update operation will return an instance of the "SafeModeResult" class, and you can verify the "DocumentsAffected" property to ensure the intended document was indeed updated. Note: Please remember that an Update method might return a null instance instead of an "SafeModeResult" instance when safe mode is not enabled. Useful Community Articles Comments about how MongoDB works and how that might affect your application: http://ethangunderson.com/blog/two-reasons-to-not-use-mongodb/ FourSquare using MongoDB had serious scalability problems: http://mashable.com/2010/10/07/mongodb-foursquare/ Is MongoDB a replacement for Memcached? http://www.quora.com/Is-MongoDB-a-good-replacement-for-Memcached/answer/Rick-Branson MongoDB Introduction, shell, when not to use, maintenance, upgrade, backups, memory, sharding, etc: http://www.markus-gattol.name/ws/mongodb.html MongoDB Collection level locking support: https://jira.mongodb.org/browse/SERVER-1240 MongoDB performance tips: http://www.quora.com/MongoDB/What-are-some-best-practices-for-optimal-performance-of-MongoDB-particularly-for-queries-that-involve-multiple-documents Lessons learned migrating from SQL Server to MongoDB: http://www.wireclub.com/development/TqnkQwQ8CxUYTVT90/read MongoDB replication performance: http://benshepheard.blogspot.com.ar/2011/01/mongodb-replication-performance.html

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  • Spending the summer at camp… Web Camp, that is

    - by Jon Galloway
    Microsoft is sponsoring a series of Web Camps this summer. They’re a series of free two day events being held worldwide, and I’m really excited about being taking part. The camp is targeted at a broad range of developer background and experience. Content builds from 101 level introductory material to 200-300 level coverage, but we hit some advanced bits (e.g. MVC 2 features, jQuery templating, IIS 7 features, etc.) that advanced developers may not yet have seen. We start with a lap around ASP.NET & Web Forms, then move on to building and application with ASP.NET MVC 2, jQuery, and Entity Framework 4, and finally deploy to IIS. I got to spend some time working with James before the first Web Camp refining the content, and I think he’s packed about as much goodness into the time available as is scientifically possible. The content is really code focused – we start with File/New Project and spend the day building a real, working application. The second day of the Web Camp provides attendees an opportunity to get hands on. There are two options: Join a team and build an application of your choice Work on a lab or tutorial James Senior and I kicked off the fun with the first Web Camp in Toronto a few weeks ago. It was sold out, lots of fun, and by all accounts a great way to spend two days. I’m really enthusiastic about the format. Rather than just listening to speakers and then forgetting everything in a few days, attendees actually build something of their choice. They get an opportunity to pitch projects they’re interested in, form teams, and build it – getting experience with “real world” problems, with all the help they need from experienced developers. James got help on the second day practical part from the good folks that run Startup Weekend. Startup Weekend is a fantastic program that gathers developers together to build cool apps in a weekend, so their input on how to organize successful teams for weekend projects was invaluable. Nick Seguin joined us in Toronto, and in addition to making sure that everything flowed smoothly, he just added a lot of fun and excitement to the event, reminding us all about how much fun it is to come up with a cool idea and just build it. In addition to the Toronto camp, I’ll be at the Mountain View, London, Munich, and New York camps over the next month. London is sold out, but the rest still have space available, so come join us! Here’s the full list, with the ones I’ll be at bolded because - you know - it’s my blog. The the whole speaker list is great, including Scott Guthrie, Scott Hanselman, James Senior, Rachel Appel, Dan Wahlin, and Christian Wenz. Toronto May 7-8 (James Senior and I were thrown out on our collective ears) Moscow May 19 Beijing May 21-22 Shanghai May 24-25 Mountain View May 27-28 (I’m speaking with Rachel Appel) Sydney May 28-29 Singapore June 04-05 London June 04-05 (I’m speaking with Christian Wenz – SOLD OUT) Munich June 07-08 (I’m speaking with Christian Wenz) Chicago June 11-12 Redmond, WA June 18-19 New York June 25-26 (I’m speaking with Dan Wahlin) Come say hi!

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  • The Evolution Of C#

    - by Paulo Morgado
    The first release of C# (C# 1.0) was all about building a new language for managed code that appealed, mostly, to C++ and Java programmers. The second release (C# 2.0) was mostly about adding what wasn’t time to built into the 1.0 release. The main feature for this release was Generics. The third release (C# 3.0) was all about reducing the impedance mismatch between general purpose programming languages and databases. To achieve this goal, several functional programming features were added to the language and LINQ was born. Going forward, new trends are showing up in the industry and modern programming languages need to be more: Declarative With imperative languages, although having the eye on the what, programs need to focus on the how. This leads to over specification of the solution to the problem in hand, making next to impossible to the execution engine to be smart about the execution of the program and optimize it to run it more efficiently (given the hardware available, for example). Declarative languages, on the other hand, focus only on the what and leave the how to the execution engine. LINQ made C# more declarative by using higher level constructs like orderby and group by that give the execution engine a much better chance of optimizing the execution (by parallelizing it, for example). Concurrent Concurrency is hard and needs to be thought about and it’s very hard to shoehorn it into a programming language. Parallel.For (from the parallel extensions) looks like a parallel for because enough expressiveness has been built into C# 3.0 to allow this without having to commit to specific language syntax. Dynamic There was been lots of debate on which ones are the better programming languages: static or dynamic. The fact is that both have good qualities and users of both types of languages want to have it all. All these trends require a paradigm switch. C# is, in many ways, already a multi-paradigm language. It’s still very object oriented (class oriented as some might say) but it can be argued that C# 3.0 has become a functional programming language because it has all the cornerstones of what a functional programming language needs. Moving forward, will have even more. Besides the influence of these trends, there was a decision of co-evolution of the C# and Visual Basic programming languages. Since its inception, there was been some effort to position C# and Visual Basic against each other and to try to explain what should be done with each language or what kind of programmers use one or the other. Each language should be chosen based on the past experience and familiarity of the developer/team/project/company and not by particular features. In the past, every time a feature was added to one language, the users of the other wanted that feature too. Going forward, when a feature is added to one language, the other will work hard to add the same feature. This doesn’t mean that XML literals will be added to C# (because almost the same can be achieved with LINQ To XML), but Visual Basic will have auto-implemented properties. Most of these features require or are built on top of features of the .NET Framework and, the focus for C# 4.0 was on dynamic programming. Not just dynamic types but being able to talk with anything that isn’t a .NET class. Also introduced in C# 4.0 is co-variance and contra-variance for generic interfaces and delegates. Stay tuned for more on the new C# 4.0 features.

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  • MVC 2 jQuery Client-side Validation

    - by nmarun
    Well, I watched Phil Haack’s show What's New in Microsoft ASP.NET MVC 2 and was impressed about the client-side validation (starts at 17:45) that MVC 2 offers. I tried creating the same, but Phil does not show what .js files need to be included and also I was not able to find the source code for the application that he used. In order to find out the required JavaScript file references, I added all of the files in my application to the page and ran it. Of course it worked, but this is definitely not an optimum solution. By removing one at a time and testing the app, I’ve short-listed the following ones: 1: <script src="../../Scripts/jquery-1.4.1.min.js" type="text/javascript"></script 2: <script src="../../Scripts/MicrosoftAjax.js" type="text/javascript"></script> 3: <script src="../../Scripts/MicrosoftMvcValidation.js" type="text/javascript"></script> Now, a little about the feature itself. Say, I’m working with a Book application so my model will look something like: 1: public class Book 2: { 3: [HiddenInput(DisplayValue = false)] 4: public int BookId { get; set; } 5:  6: [DisplayName("Book Title")] 7: [Required(ErrorMessage = "Book title is required")] 8: [StringLength(20, ErrorMessage = "Must be under 20 characters")] 9: public string Title { get; set; } 10:  11: [Required(ErrorMessage = "Author is required")] 12: [StringLength(40, ErrorMessage = "Must be under 40 characters")] 13: public string Author { get; set; } 14:  15: public decimal Price { get; set; } 16: 17: [DisplayName("ISBN")] 18: [StringLength(13, ErrorMessage = "Must be 13 characters")] 19: public string Isbn { get; set; } 20: } This ensures that the data passed will be validated upon post. But what would happen if you add the line (along with the above mentioned .js files): 1: <% Html.EnableClientValidation(); %> Now, this acts as ‘on-the-fly’ or ‘real-time’ validation. Now, when the user types 20 characters for the Title, the error shows up right on the 21st character. Beautiful… and you do not have to create the JavaScript function(s) for this. They’re auto-magically created for you. (Doing a ‘View Source’ on the browser page shows you the JavaScript logic that goes on behind the scenes). I bumped into another post that shows how .net 4 allows us to create custom validation attributes: Dynamic Range validation in MVC 2. This will help us attach virtually any business logic to the model itself. Please see the source code I’ve worked with.

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  • Windows Workflow Foundation (WF) and things I were more intuitive

    - by pjohnson
    I've started using Windows Workflow Foundation, and so far ran into a few things that aren't incredibly obvious. Microsoft did a good job of providing a ton of samples, which is handy because you need them to get anywhere with WF. The docs are thin, so I've been bouncing between samples and downloadable labs to figure out how to implement various activities in a workflow. Code separation or not? You can create a workflow and activity in Visual Studio with or without code separation, i.e. just a .cs "Component" style object with a Designer.cs file, or a .xoml XML markup file with code behind (beside?) it. Absence any obvious advantage to one or the other, I used code separation for workflows and any complex custom activities, and without code separation for custom activities that just inherit from the Activity class and thus don't have anything special in the designer. So far, so good. Service - In the WF world, this is simply a class that talks to the workflow about things outside the workflow, not to be confused with how the term "service" is used in every other context I've seen in the Windows and .NET world, i.e. an executable that waits for events or requests from a client and services them (Windows service, web service, WCF service, etc.). ListenActivity - Such a great concept, yet so unintuitive. It seems you need at least two branches (EventDrivenActivity instances), one for your positive condition and one for a timeout. The positive condition has a HandleExternalEventActivity, and the timeout has a DelayActivity followed by however you want to handle the delay, e.g. a ThrowActivity. The timeout is simple enough; wiring up the HandleExternalEventActivity is where things get fun. You need to create a service (see above), and an interface for that service (this seems more complex than should be necessary--why not have activities just wire to a service directly?). And you need to create a custom EventArgs class that inherits from ExternalDataEventArgs--you can't create an ExternalDataEventArgs event handler directly, even if you don't need to add any more information to the event args, despite ExternalDataEventArgs not being marked as an abstract class, nor a compiler error nor warning nor any other indication that you're doing something wrong, until you run it and find that it always times out and get to check every place mentioned here to see why. Your interface and service need an event that consumes your custom EventArgs class, and a method to fire that event. You need to call that method from somewhere. Then you get to hope that you did everything just right, or that you can step through code in the debugger before your Delay timeout expires. Yes, it's as much fun as it sounds. TransactionScopeActivity - I had the bright idea of putting one in as a placeholder, then filling in the database updates later. That caused this error: The workflow hosting environment does not have a persistence service as required by an operation on the workflow instance "[GUID]". ...which is about as helpful as "Object reference not set to an instance of an object" and even more fun to debug. Google led me to this Microsoft Forums hit, and from there I figured out it didn't like that the activity had no children. Again, a Validator on TransactionScopeActivity would have pointed this out to me at design time, rather than handing me a nearly useless error at runtime. Easily enough, I disabled the activity and that fixed it. I still see huge potential in my work where WF could make things easier and more flexible, but there are some seriously rough edges at the moment. Maybe I'm just spoiled by how much easier and more intuitive development elsewhere in the .NET Framework is.

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  • Session and Pop Up Window

    - by imran_ku07
     Introduction :        Session is the secure state management. It allows the user to store their information in one page and access in another page. Also it is so much powerful that store any type of object. Every user's session is identified by their cookie, which client presents to server. But unfortunately when you open a new pop up window, this cookie is not post to server with request, due to which server is unable to identify the session data for current user.         In this Article i will show you how to handle this situation,  Description :         During working in a application, i was getting an Exception saying that Session is null, when a pop window opens. After seeing the problem more closely i found that ASP.NET_SessionId cookie for parent page is not post in cookie header of child (popup) window.         Therefore for making session present in both parent and child (popup) window, you have to present same cookie. For cookie sharing i passed parent SessionID in query string,   window.open('http://abc.com/s.aspx?SASID=" & Session.SessionID &','V');           and in Application_PostMapRequestHandler application Event, check if the current request has no ASP.NET_SessionId cookie and SASID query string is not null then add this cookie to Request before Session is acquired, so that Session data remain same for both parent and popup window.    Private Sub Application_PostMapRequestHandler(ByVal sender As Object, ByVal e As EventArgs)           If (Request.Cookies("ASP.NET_SessionId") Is Nothing) AndAlso (Request.QueryString("SASID") IsNot Nothing) Then               Request.Cookies.Add(New HttpCookie("ASP.NET_SessionId", Request.QueryString("SASID")))           End If       End Sub           Now access Session in your parent and child window without any problem. How this works :          ASP.NET (both Web Form or MVC) uses a cookie (ASP.NET_SessionId) to identify the user who is requesting. Cookies are may be persistent (saved permanently in user cookies ) or non-persistent (saved temporary in browser memory). ASP.NET_SessionId cookie saved as non-persistent. This means that if the user closes the browser, the cookie is immediately removed. This is a sensible step that ensures security. That's why ASP.NET unable to identify that the request is coming from the same user. Therefore every browser instance get it's own ASP.NET_SessionId. To resolve this you need to present the same parent ASP.NET_SessionId cookie to the server when open a popup window.           You can confirm this situation by using some tools like Firebug, Fiddler,  Summary :          Hopefully you will enjoy after reading this article, by seeing that how to workaround the problem of sharing Session between different browser instances by sharing their Session identifier Cookie.

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  • Fun with Python

    - by dotneteer
    I am taking a class on Coursera recently. My formal education is in physics. Although I have been working as a developer for over 18 years and have learnt a lot of programming on the job, I still would like to gain some systematic knowledge in computer science. Coursera courses taught by Standard professors provided me a wonderful chance. The three languages recommended for assignments are Java, C and Python. I am fluent in Java and have done some projects using C++/MFC/ATL in the past, but I would like to try something different this time. I first started with pure C. Soon I discover that I have to write a lot of code outside the question that I try to solve because the very limited C standard library. For example, to read a list of values from a file, I have to read characters by characters until I hit a delimiter. If I need a list that can grow, I have to create a data structure myself, something that I have taking for granted in .Net or Java. Out of frustration, I switched to Python. I was pleasantly surprised to find that Python is very easy to learn. The tutorial on the official Python site has the exactly the right pace for me, someone with experience in another programming. After a couple of hours on the tutorial and a few more minutes of toying with IDEL, I was in business. I like the “battery supplied” philosophy that gives everything that I need out of box. For someone from C# or Java background, curly braces are replaced by colon(:) and tab spaces. Although I tend to miss colon from time to time, I found that the idea of tab space is actually very nice once I get use to them. I also like to feature of multiple assignment and multiple return parameters. When I need to return a by-product, I just add it to the list of returns. When would use Python? I would use Python if I need to computer anything quick. The language is very easy to use. Python has a good collection of libraries (packages). The REPL of the interpreter allows me test ideas quickly before committing them into script. Lots of computer science work have been ported from Lisp to Python. Some universities are even teaching SICP in Python. When wouldn’t I use Python? I mostly would not use it in a managed environment, such as Ironpython or Jython. Both .Net and Java already have a rich library so one has to make a choice which library to use. If we use the managed runtime library, the code will tie to the particular runtime and thus not portable. If we use the Python library, then we will face the relatively long start-up time. For this reason, I would not recommend to use Ironpython for WP7 development. The only situation that I see merit with managed Python is in a server application where I can preload Python so that the start-up time is not a concern. Using Python as a managed glue language is an over-kill most of the time. A managed Scheme could be a better glue language as it is small enough to start-up very fast.

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  • What's happening in Red Gate's .NET Developer Tools division?

    .NET 4.0, Silverlight 4, F# decompilation in .NET Reflector, our crazy shipping schedule, and some prize draw winners. Yes, with a list of topics that broad, it can only be another update on what's happening in Red Gate's .NET Developer Tools division....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • A review of the latest version of Crypto Obfuscator for .NET and its features.

    Crypto Obfuscator For .Net is a powerful and easy-to-use product for code protection, deployment and optimization of your your .Net software. A review of the latest version of Crypto Obfuscator for .NET and its features.  read moreBy Peter BrombergDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • after enabling mod ssl apache stops listening on port 80

    - by zensys
    I have an ubuntu 12.04 server with zend server CE installed. I now wanted to enable https but after the first steps according to the documentation, 'a2enmod ssl' and 'apache service restart', apache does not listen on 443 but neither on 80, according to netstat -tap | grep http(s)! This is what I see in my error log, but I can't make much of it: [Fri May 25 19:52:39 2012] [notice] caught SIGTERM, shutting down [Fri May 25 19:52:41 2012] [warn] Init: Session Cache is not configured [hint: SSLSessionCache] [Fri May 25 19:52:41 2012] [notice] ModSecurity for Apache/2.6.3 (http://www.modsecurity.org/) configured. [Fri May 25 19:52:41 2012] [notice] ModSecurity: APR compiled version="1.4.5"; loaded version="1.4.6" [Fri May 25 19:52:41 2012] [warn] ModSecurity: Loaded APR do not match with compiled! [Fri May 25 19:52:41 2012] [notice] ModSecurity: PCRE compiled version="8.12"; loaded version="8.12 2011-01-15" [Fri May 25 19:52:41 2012] [notice] ModSecurity: LUA compiled version="Lua 5.1" [Fri May 25 19:52:41 2012] [notice] ModSecurity: LIBXML compiled version="2.7.8" [Fri May 25 19:53:11 2012] [notice] ModSecurity for Apache/2.6.3 (http://www.modsecurity.org/) configured. [Fri May 25 19:53:11 2012] [notice] ModSecurity: APR compiled version="1.4.5"; loaded version="1.4.6" [Fri May 25 19:53:11 2012] [warn] ModSecurity: Loaded APR do not match with compiled! [Fri May 25 19:53:11 2012] [notice] ModSecurity: PCRE compiled version="8.12"; loaded version="8.12 2011-01-15" [Fri May 25 19:53:11 2012] [notice] ModSecurity: LUA compiled version="Lua 5.1" [Fri May 25 19:53:11 2012] [notice] ModSecurity: LIBXML compiled version="2.7.8" [Fri May 25 19:53:12 2012] [notice] Apache/2.2.22 (Ubuntu) PHP/5.3.8-ZS5.5.0 configured -- resuming normal operations and here is my httpd.conf: # Name based virtual hosting <virtualhost *:80> ServerName www-redirect KeepAlive Off RewriteEngine On RewriteCond %{HTTP_HOST} ^[^\./]+\.[^\./]+$ RewriteRule ^/(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L] </virtualhost> Alias /shared/js "/home/web/library/js" Alias /shared/image "/home/web/library/image" <IfModule mod_expires.c> <FilesMatch "\.(jpe?g|png|gif|js|css|doc|rtf|xls|pdf)$"> ExpiresActive On ExpiresDefault "access plus 1 week" </FilesMatch> </IfModule> ErrorLog ${APACHE_LOG_DIR}/error.log LogLevel warn <Directory /> Options FollowSymLinks AllowOverride None Order allow,deny allow from all </Directory> <Location /> RewriteEngine On RewriteCond %{REQUEST_FILENAME} -s [OR] RewriteCond %{REQUEST_FILENAME} -l [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^.*$ - [NC,L] RewriteRule ^.*$ /index.php [NC,L] </Location> netstat -tap gives: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 *:mysql *:* LISTEN 765/mysqld tcp 0 0 *:pop3 *:* LISTEN 744/dovecot tcp 0 0 *:imap2 *:* LISTEN 744/dovecot tcp 0 0 *:http *:* LISTEN 19861/apache2 tcp 0 0 *:smtp *:* LISTEN 30365/master tcp 0 0 *:4444 *:* LISTEN 634/sshd tcp 0 0 *:kamanda *:* LISTEN 1167/lighttpd tcp 0 0 *:imaps *:* LISTEN 744/dovecot tcp 0 0 *:amandaidx *:* LISTEN 1167/lighttpd tcp 0 0 localhost.loc:amidxtape *:* LISTEN 19861/apache2 tcp 0 0 *:pop3s *:* LISTEN 744/dovecot tcp 0 384 mail.mysite.:4444 231.214.14.37.dyn:41909 ESTABLISHED 19039/sshd: web [pr tcp 0 0 localhost.localdo:mysql localhost.localdo:48252 ESTABLISHED 765/mysqld tcp 0 0 mail.mysite.:http 231.214.14.37.dyn:54686 TIME_WAIT - tcp 0 0 mail.mysite.:4444 231.214.14.37.dyn:42419 ESTABLISHED 19372/sshd: web [pr tcp 0 0 localhost.localdo:48252 localhost.localdo:mysql ESTABLISHED 19884/auth tcp 0 0 mail.mysite.:http 231.214.14.37.dyn:54685 TIME_WAIT - tcp6 0 0 [::]:pop3 [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:imap2 [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:smtp [::]:* LISTEN 30365/master tcp6 0 0 [::]:4444 [::]:* LISTEN 634/sshd tcp6 0 0 [::]:imaps [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:pop3s [::]:* LISTEN 744/dovecot Anyone knows what I am doing wrong? Perhaps I should take some additional steps to make apache listen 0n 443 but that it stops listening on 80 altogether I can't understand.

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  • Simple Cisco ASA 5505 config issue

    - by Ben Sebborn
    I have a Cisco ASA setup with two interfaces: inside: 192.168.2.254 / 255.255.255.0 SecLevel:100 outside: 192.168.3.250 / 255.255.255.0 SecLevel: 0 I have a static route setup to allow PCs on the inside network to access the internet via a gateway on the outside interface (3.254): outside 0.0.0.0 0.0.0.0 192.168.3.254 This all works fine. I now need to be able to access a PC on the outside interface (3.253) from a PC on the inside interface on port 35300. I understand I should be able to do this with no problems, as I'm going from a higher security level to a lower one. However I can't get any connection. Do I need to set up a seperate static route? Perhaps the route above is overriding what I need to be able to do (is it routing ALL traffic through the gateway?) Any advice on how to do this would be apprecaited. I am configuring this via ASDM but the config can be seen as below: Result of the command: "show running-config" : Saved : ASA Version 8.2(5) ! hostname ciscoasa domain-name xxx.internal names name 192.168.2.201 dev.xxx.internal description Internal Dev server name 192.168.2.200 Newserver ! interface Ethernet0/0 switchport access vlan 2 ! interface Ethernet0/1 ! interface Ethernet0/2 ! interface Ethernet0/3 shutdown ! interface Ethernet0/4 shutdown ! interface Ethernet0/5 shutdown ! interface Ethernet0/6 shutdown ! interface Ethernet0/7 shutdown ! interface Vlan1 nameif inside security-level 100 ip address 192.168.2.254 255.255.255.0 ! interface Vlan2 nameif outside security-level 0 ip address 192.168.3.250 255.255.255.0 ! ! time-range Workingtime periodic weekdays 9:00 to 18:00 ! ftp mode passive clock timezone GMT/BST 0 clock summer-time GMT/BDT recurring last Sun Mar 1:00 last Sun Oct 2:00 dns domain-lookup inside dns server-group DefaultDNS name-server Newserver domain-name xxx.internal same-security-traffic permit inter-interface object-group service Mysql tcp port-object eq 3306 object-group protocol TCPUDP protocol-object udp protocol-object tcp access-list inside_access_in extended permit ip any any access-list outside_access_in remark ENABLES OUTSDIE ACCESS TO DEV SERVER! access-list outside_access_in extended permit tcp any interface outside eq www time-range Workingtime inactive access-list outside_access_in extended permit tcp host www-1.xxx.com interface outside eq ssh access-list inside_access_in_1 extended permit tcp any any eq www access-list inside_access_in_1 extended permit tcp any any eq https access-list inside_access_in_1 remark Connect to SSH services access-list inside_access_in_1 extended permit tcp any any eq ssh access-list inside_access_in_1 remark Connect to mysql server access-list inside_access_in_1 extended permit tcp any host mysql.xxx.com object-group Mysql access-list inside_access_in_1 extended permit tcp any host mysql.xxx.com eq 3312 access-list inside_access_in_1 extended permit object-group TCPUDP host Newserver any eq domain access-list inside_access_in_1 extended permit icmp any any access-list inside_access_in_1 remark Draytek Admin access-list inside_access_in_1 extended permit tcp any 192.168.3.0 255.255.255.0 eq 4433 access-list inside_access_in_1 remark Phone System access-list inside_access_in_1 extended permit tcp any 192.168.3.0 255.255.255.0 eq 35300 log disable pager lines 24 logging enable logging asdm warnings logging from-address [email protected] logging recipient-address [email protected] level errors mtu inside 1500 mtu outside 1500 ip verify reverse-path interface inside ip verify reverse-path interface outside ipv6 access-list inside_access_ipv6_in permit tcp any any eq www ipv6 access-list inside_access_ipv6_in permit tcp any any eq https ipv6 access-list inside_access_ipv6_in permit tcp any any eq ssh ipv6 access-list inside_access_ipv6_in permit icmp6 any any icmp unreachable rate-limit 1 burst-size 1 icmp permit any outside no asdm history enable arp timeout 14400 global (outside) 1 interface nat (inside) 1 0.0.0.0 0.0.0.0 static (inside,outside) tcp interface www dev.xxx.internal www netmask 255.255.255.255 static (inside,outside) tcp interface ssh dev.xxx.internal ssh netmask 255.255.255.255 access-group inside_access_in in interface inside control-plane access-group inside_access_in_1 in interface inside access-group inside_access_ipv6_in in interface inside access-group outside_access_in in interface outside route outside 0.0.0.0 0.0.0.0 192.168.3.254 10 route outside 192.168.3.252 255.255.255.255 192.168.3.252 1 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 timeout floating-conn 0:00:00 dynamic-access-policy-record DfltAccessPolicy aaa authentication telnet console LOCAL aaa authentication enable console LOCAL

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  • how limit the number of open TCP streams from same IP to a local port?

    - by JMW
    Hi, i would like to limit the number of concurrent open TCP streams from the the same IP to the server's (local) port. Let's say 4 concurrent conncetions. How can this be done with ip tables? the closest thing, that i've found was: In Apache, is there a way to limit the number of new connections per second/hour/day? iptables -A INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --set iptables -A INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --update --seconds 86400 --hitcount 100 -j REJECT But this limitation just messures the number of new connections over the time. This might be good for controlling HTTP traffic. But this is not a good solution for me, since my TCP streams usually have a lifetime between 5 minutes and 2 hours. thanks a lot in advance for any reply :)

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5 Part 1: Table per Hierarchy (TPH)

    - by mortezam
    A simple strategy for mapping classes to database tables might be “one table for every entity persistent class.” This approach sounds simple enough and, indeed, works well until we encounter inheritance. Inheritance is such a visible structural mismatch between the object-oriented and relational worlds because object-oriented systems model both “is a” and “has a” relationships. SQL-based models provide only "has a" relationships between entities; SQL database management systems don’t support type inheritance—and even when it’s available, it’s usually proprietary or incomplete. There are three different approaches to representing an inheritance hierarchy: Table per Hierarchy (TPH): Enable polymorphism by denormalizing the SQL schema, and utilize a type discriminator column that holds type information. Table per Type (TPT): Represent "is a" (inheritance) relationships as "has a" (foreign key) relationships. Table per Concrete class (TPC): Discard polymorphism and inheritance relationships completely from the SQL schema.I will explain each of these strategies in a series of posts and this one is dedicated to TPH. In this series we'll deeply dig into each of these strategies and will learn about "why" to choose them as well as "how" to implement them. Hopefully it will give you a better idea about which strategy to choose in a particular scenario. Inheritance Mapping with Entity Framework Code FirstAll of the inheritance mapping strategies that we discuss in this series will be implemented by EF Code First CTP5. The CTP5 build of the new EF Code First library has been released by ADO.NET team earlier this month. EF Code-First enables a pretty powerful code-centric development workflow for working with data. I’m a big fan of the EF Code First approach, and I’m pretty excited about a lot of productivity and power that it brings. When it comes to inheritance mapping, not only Code First fully supports all the strategies but also gives you ultimate flexibility to work with domain models that involves inheritance. The fluent API for inheritance mapping in CTP5 has been improved a lot and now it's more intuitive and concise in compare to CTP4. A Note For Those Who Follow Other Entity Framework ApproachesIf you are following EF's "Database First" or "Model First" approaches, I still recommend to read this series since although the implementation is Code First specific but the explanations around each of the strategies is perfectly applied to all approaches be it Code First or others. A Note For Those Who are New to Entity Framework and Code-FirstIf you choose to learn EF you've chosen well. If you choose to learn EF with Code First you've done even better. To get started, you can find a great walkthrough by Scott Guthrie here and another one by ADO.NET team here. In this post, I assume you already setup your machine to do Code First development and also that you are familiar with Code First fundamentals and basic concepts. You might also want to check out my other posts on EF Code First like Complex Types and Shared Primary Key Associations. A Top Down Development ScenarioThese posts take a top-down approach; it assumes that you’re starting with a domain model and trying to derive a new SQL schema. Therefore, we start with an existing domain model, implement it in C# and then let Code First create the database schema for us. However, the mapping strategies described are just as relevant if you’re working bottom up, starting with existing database tables. I’ll show some tricks along the way that help you dealing with nonperfect table layouts. Let’s start with the mapping of entity inheritance. -- The Domain ModelIn our domain model, we have a BillingDetail base class which is abstract (note the italic font on the UML class diagram below). We do allow various billing types and represent them as subclasses of BillingDetail class. As for now, we support CreditCard and BankAccount: Implement the Object Model with Code First As always, we start with the POCO classes. Note that in our DbContext, I only define one DbSet for the base class which is BillingDetail. Code First will find the other classes in the hierarchy based on Reachability Convention. public abstract class BillingDetail  {     public int BillingDetailId { get; set; }     public string Owner { get; set; }             public string Number { get; set; } } public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } } public class CreditCard : BillingDetail {     public int CardType { get; set; }                     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } } public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; } } This object model is all that is needed to enable inheritance with Code First. If you put this in your application you would be able to immediately start working with the database and do CRUD operations. Before going into details about how EF Code First maps this object model to the database, we need to learn about one of the core concepts of inheritance mapping: polymorphic and non-polymorphic queries. Polymorphic Queries LINQ to Entities and EntitySQL, as object-oriented query languages, both support polymorphic queries—that is, queries for instances of a class and all instances of its subclasses, respectively. For example, consider the following query: IQueryable<BillingDetail> linqQuery = from b in context.BillingDetails select b; List<BillingDetail> billingDetails = linqQuery.ToList(); Or the same query in EntitySQL: string eSqlQuery = @"SELECT VAlUE b FROM BillingDetails AS b"; ObjectQuery<BillingDetail> objectQuery = ((IObjectContextAdapter)context).ObjectContext                                                                          .CreateQuery<BillingDetail>(eSqlQuery); List<BillingDetail> billingDetails = objectQuery.ToList(); linqQuery and eSqlQuery are both polymorphic and return a list of objects of the type BillingDetail, which is an abstract class but the actual concrete objects in the list are of the subtypes of BillingDetail: CreditCard and BankAccount. Non-polymorphic QueriesAll LINQ to Entities and EntitySQL queries are polymorphic which return not only instances of the specific entity class to which it refers, but all subclasses of that class as well. On the other hand, Non-polymorphic queries are queries whose polymorphism is restricted and only returns instances of a particular subclass. In LINQ to Entities, this can be specified by using OfType<T>() Method. For example, the following query returns only instances of BankAccount: IQueryable<BankAccount> query = from b in context.BillingDetails.OfType<BankAccount>() select b; EntitySQL has OFTYPE operator that does the same thing: string eSqlQuery = @"SELECT VAlUE b FROM OFTYPE(BillingDetails, Model.BankAccount) AS b"; In fact, the above query with OFTYPE operator is a short form of the following query expression that uses TREAT and IS OF operators: string eSqlQuery = @"SELECT VAlUE TREAT(b as Model.BankAccount)                       FROM BillingDetails AS b                       WHERE b IS OF(Model.BankAccount)"; (Note that in the above query, Model.BankAccount is the fully qualified name for BankAccount class. You need to change "Model" with your own namespace name.) Table per Class Hierarchy (TPH)An entire class hierarchy can be mapped to a single table. This table includes columns for all properties of all classes in the hierarchy. The concrete subclass represented by a particular row is identified by the value of a type discriminator column. You don’t have to do anything special in Code First to enable TPH. It's the default inheritance mapping strategy: This mapping strategy is a winner in terms of both performance and simplicity. It’s the best-performing way to represent polymorphism—both polymorphic and nonpolymorphic queries perform well—and it’s even easy to implement by hand. Ad-hoc reporting is possible without complex joins or unions. Schema evolution is straightforward. Discriminator Column As you can see in the DB schema above, Code First has to add a special column to distinguish between persistent classes: the discriminator. This isn’t a property of the persistent class in our object model; it’s used internally by EF Code First. By default, the column name is "Discriminator", and its type is string. The values defaults to the persistent class names —in this case, “BankAccount” or “CreditCard”. EF Code First automatically sets and retrieves the discriminator values. TPH Requires Properties in SubClasses to be Nullable in the Database TPH has one major problem: Columns for properties declared by subclasses will be nullable in the database. For example, Code First created an (INT, NULL) column to map CardType property in CreditCard class. However, in a typical mapping scenario, Code First always creates an (INT, NOT NULL) column in the database for an int property in persistent class. But in this case, since BankAccount instance won’t have a CardType property, the CardType field must be NULL for that row so Code First creates an (INT, NULL) instead. If your subclasses each define several non-nullable properties, the loss of NOT NULL constraints may be a serious problem from the point of view of data integrity. TPH Violates the Third Normal FormAnother important issue is normalization. We’ve created functional dependencies between nonkey columns, violating the third normal form. Basically, the value of Discriminator column determines the corresponding values of the columns that belong to the subclasses (e.g. BankName) but Discriminator is not part of the primary key for the table. As always, denormalization for performance can be misleading, because it sacrifices long-term stability, maintainability, and the integrity of data for immediate gains that may be also achieved by proper optimization of the SQL execution plans (in other words, ask your DBA). Generated SQL QueryLet's take a look at the SQL statements that EF Code First sends to the database when we write queries in LINQ to Entities or EntitySQL. For example, the polymorphic query for BillingDetails that you saw, generates the following SQL statement: SELECT  [Extent1].[Discriminator] AS [Discriminator],  [Extent1].[BillingDetailId] AS [BillingDetailId],  [Extent1].[Owner] AS [Owner],  [Extent1].[Number] AS [Number],  [Extent1].[BankName] AS [BankName],  [Extent1].[Swift] AS [Swift],  [Extent1].[CardType] AS [CardType],  [Extent1].[ExpiryMonth] AS [ExpiryMonth],  [Extent1].[ExpiryYear] AS [ExpiryYear] FROM [dbo].[BillingDetails] AS [Extent1] WHERE [Extent1].[Discriminator] IN ('BankAccount','CreditCard') Or the non-polymorphic query for the BankAccount subclass generates this SQL statement: SELECT  [Extent1].[BillingDetailId] AS [BillingDetailId],  [Extent1].[Owner] AS [Owner],  [Extent1].[Number] AS [Number],  [Extent1].[BankName] AS [BankName],  [Extent1].[Swift] AS [Swift] FROM [dbo].[BillingDetails] AS [Extent1] WHERE [Extent1].[Discriminator] = 'BankAccount' Note how Code First adds a restriction on the discriminator column and also how it only selects those columns that belong to BankAccount entity. Change Discriminator Column Data Type and Values With Fluent API Sometimes, especially in legacy schemas, you need to override the conventions for the discriminator column so that Code First can work with the schema. The following fluent API code will change the discriminator column name to "BillingDetailType" and the values to "BA" and "CC" for BankAccount and CreditCard respectively: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) {     modelBuilder.Entity<BillingDetail>()                 .Map<BankAccount>(m => m.Requires("BillingDetailType").HasValue("BA"))                 .Map<CreditCard>(m => m.Requires("BillingDetailType").HasValue("CC")); } Also, changing the data type of discriminator column is interesting. In the above code, we passed strings to HasValue method but this method has been defined to accepts a type of object: public void HasValue(object value); Therefore, if for example we pass a value of type int to it then Code First not only use our desired values (i.e. 1 & 2) in the discriminator column but also changes the column type to be (INT, NOT NULL): modelBuilder.Entity<BillingDetail>()             .Map<BankAccount>(m => m.Requires("BillingDetailType").HasValue(1))             .Map<CreditCard>(m => m.Requires("BillingDetailType").HasValue(2)); SummaryIn this post we learned about Table per Hierarchy as the default mapping strategy in Code First. The disadvantages of the TPH strategy may be too serious for your design—after all, denormalized schemas can become a major burden in the long run. Your DBA may not like it at all. In the next post, we will learn about Table per Type (TPT) strategy that doesn’t expose you to this problem. References ADO.NET team blog Java Persistence with Hibernate book a { text-decoration: none; } a:visited { color: Blue; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } p.MsoNormal { margin-top: 0in; margin-right: 0in; margin-bottom: 10.0pt; margin-left: 0in; line-height: 115%; font-size: 11.0pt; font-family: "Calibri" , "sans-serif"; }

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  • Fun with RadCaptcha for ASP.NET AJAX and OCR software

    A friend of mine was evaluating OCR software and finally decided to go with FineReader. I was curious what would happen if we put the RadCaptcha control in. Will the advanced OCR manage to decode it or not? At first he showed me a test run with the RadCaptcha demo description, to get an idea of the basic output:    Naturally, the captured description text was no problem - only a few characters were misread but then corrected with the spellcheck. Next, the real test was performed:    These were only a couple of the results, but there is no need to post the rest of the tests - none of the RadCaptcha images were recognized by the OCR software. Here are the CaptchaImage settings used in the tests: Background Noise Level: Low /default value Line Noise Level: Low /default value Font Warp Factor: Low /Medium is default value...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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