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  • Prefer extension methods for encapsulation and reusability?

    - by tzaman
    edit4: wikified, since this seems to have morphed more into a discussion than a specific question. In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. (edit: Even in the current .NET library, I can see places where it would've been useful to have extensions instead of instance methods - for example, all of the utility functions of List<T> (Sort, BinarySearch, FindIndex, etc.) would be incredibly useful if they were lifted up to IList<T> - getting free bonus functionality like that adds a lot more benefit to implementing the interface.) So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself? (edit2: In response to Tomas - while C# did start out with Java's (overly, imo) OO mentality, it seems to be embracing more multi-paradigm programming with every new release; the main thrust of this question is whether using extension methods to drive a style change (towards more generic / functional C#) is useful or worthwhile..) edit3: overridable extension methods The only real problem identified so far with this approach, is that you can't specialize extension methods if you need to. I've been thinking about the issue, and I think I've come up with a solution. Suppose I have an interface MyInterface, which I want to extend - I define my extension methods in a MyExtension static class, and pair it with another interface, call it MyExtensionOverrider. MyExtension methods are defined according to this pattern: public static int MyMethod(this MyInterface obj, int arg, bool attemptCast=true) { if (attemptCast && obj is MyExtensionOverrider) { return ((MyExtensionOverrider)obj).MyMethod(arg); } // regular implementation here } The override interface mirrors all of the methods defined in MyExtension, except without the this or attemptCast parameters: public interface MyExtensionOverrider { int MyMethod(int arg); string MyOtherMethod(); } Now, any class can implement the interface and get the default extension functionality: public class MyClass : MyInterface { ... } Anyone that wants to override it with specific implementations can additionally implement the override interface: public class MySpecializedClass : MyInterface, MyExtensionOverrider { public int MyMethod(int arg) { //specialized implementation for one method } public string MyOtherMethod() { // fallback to default for others MyExtension.MyOtherMethod(this, attemptCast: false); } } And there we go: extension methods provided on an interface, with the option of complete extensibility if needed. Fully general too, the interface itself doesn't need to know about the extension / override, and multiple extension / override pairs can be implemented without interfering with each other. I can see three problems with this approach - It's a little bit fragile - the extension methods and override interface have to be kept synchronized manually. It's a little bit ugly - implementing the override interface involves boilerplate for every function you don't want to specialize. It's a little bit slow - there's an extra bool comparison and cast attempt added to the mainline of every method. Still, all those notwithstanding, I think this is the best we can get until there's language support for interface functions. Thoughts?

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  • Advice needed on how to start web programming? [closed]

    - by Recursion
    Possible Duplicate: Best approach to learning web programming I have resisted doing web programming for a while, but I have come to the realization that I need to learn it and may have resisted do to fear of the unknown. I am a regular applications and systems programmer with no real idea of how to even get started. I have tried to start a few times, rails, django, tornado, web.py, cherrypy, but always get discouraged and quit. The most web programming I have done was in HTML during 1995 for my geocities site. I have pretty decent experience with regular programming in C, Python, Assembly and Java. Just looking for a way to get started and get a good overview of the different technologies and frameworks. I am not doing this for a job or employment, just to learn.

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  • Silverlight 4 + WCF RIA - Data Service Design Best Practices

    - by Chadd Nervig
    Hey all. I realize this is a rather long question, but I'd really appreciate any help from anyone experienced with RIA services. Thanks! I'm working on a Silverlight 4 app that views data from the server. I'm relatively inexperienced with RIA Services, so have been working through the tasks of getting the data I need down to the client, but every new piece I add to the puzzle seems to be more and more problematic. I feel like I'm missing some basic concepts here, and it seems like I'm just 'hacking' pieces on, in time-consuming ways, each one breaking the previous ones as I try to add them. I'd love to get the feedback of developers experienced with RIA services, to figure out the intended way to do what I'm trying to do. Let me lay out what I'm trying to do: First, the data. The source of this data is a variety of sources, primarily created by a shared library which reads data from our database, and exposes it as POCOs (Plain Old CLR Objects). I'm creating my own POCOs to represent the different types of data I need to pass between server and client. DataA - This app is for viewing a certain type of data, lets call DataA, in near-realtime. Every 3 minutes, the client should pull data down from the server, of all the new DataA since the last time it requested data. DataB - Users can view the DataA objects in the app, and may select one of them from the list, which displays additional details about that DataA. I'm bringing these extra details down from the server as DataB. DataC - One of the things that DataB contains is a history of a couple important values over time. I'm calling each data point of this history a DataC object, and each DataB object contains many DataCs. The Data Model - On the server side, I have a single DomainService: [EnableClientAccess] public class MyDomainService : DomainService { public IEnumerable<DataA> GetDataA(DateTime? startDate) { /*Pieces together the DataAs that have been created since startDate, and returns them*/ } public DataB GetDataB(int dataAID) { /*Looks up the extended info for that dataAID, constructs a new DataB with that DataA's data, plus the extended info (with multiple DataCs in a List<DataC> property on the DataB), and returns it*/ } //Not exactly sure why these are here, but I think it //wouldn't compile without them for some reason? The data //is entirely read-only, so I don't need to update. public void UpdateDataA(DataA dataA) { throw new NotSupportedException(); } public void UpdateDataB(DataB dataB) { throw new NotSupportedException(); } } The classes for DataA/B/C look like this: [KnownType(typeof(DataB))] public partial class DataA { [Key] [DataMember] public int DataAID { get; set; } [DataMember] public decimal MyDecimalA { get; set; } [DataMember] public string MyStringA { get; set; } [DataMember] public DataTime MyDateTimeA { get; set; } } public partial class DataB : DataA { [Key] [DataMember] public int DataAID { get; set; } [DataMember] public decimal MyDecimalB { get; set; } [DataMember] public string MyStringB { get; set; } [Include] //I don't know which of these, if any, I need? [Composition] [Association("DataAToC","DataAID","DataAID")] public List<DataC> DataCs { get; set; } } public partial class DataC { [Key] [DataMember] public int DataAID { get; set; } [Key] [DataMember] public DateTime Timestamp { get; set; } [DataMember] public decimal MyHistoricDecimal { get; set; } } I guess a big question I have here is... Should I be using Entities instead of POCOs? Are my classes constructed correctly to be able to pass the data down correctly? Should I be using Invoke methods instead of Query (Get) methods on the DomainService? On the client side, I'm having a number of issues. Surprisingly, one of my biggest ones has been threading. I didn't expect there to be so many threading issues with MyDomainContext. What I've learned is that you only seem to be able to create MyDomainContextObjects on the UI thread, all of the queries you can make are done asynchronously only, and that if you try to fake doing it synchronously by blocking the calling thread until the LoadOperation finishes, you have to do so on a background thread, since it uses the UI thread to make the query. So here's what I've got so far. The app should display a stream of the DataA objects, spreading each 3min chunk of them over the next 3min (so they end up displayed 3min after the occurred, looking like a continuous stream, but only have to be downloaded in 3min bursts). To do this, the main form initializes, creates a private MyDomainContext, and starts up a background worker, which continuously loops in a while(true). On each loop, it checks if it has any DataAs left over to display. If so, it displays that Data, and Thread.Sleep()s until the next DataA is scheduled to be displayed. If it's out of data, it queries for more, using the following methods: public DataA[] GetDataAs(DateTime? startDate) { _loadOperationGetDataACompletion = new AutoResetEvent(false); LoadOperation<DataA> loadOperationGetDataA = null; loadOperationGetDataA = _context.Load(_context.GetDataAQuery(startDate), System.ServiceModel.DomainServices.Client.LoadBehavior.RefreshCurrent, false); loadOperationGetDataA.Completed += new EventHandler(loadOperationGetDataA_Completed); _loadOperationGetDataACompletion.WaitOne(); List<DataA> dataAs = new List<DataA>(); foreach (var dataA in loadOperationGetDataA.Entities) dataAs.Add(dataA); return dataAs.ToArray(); } private static AutoResetEvent _loadOperationGetDataACompletion; private static void loadOperationGetDataA_Completed(object sender, EventArgs e) { _loadOperationGetDataACompletion.Set(); } Seems kind of clunky trying to force it into being synchronous, but since this already is on a background thread, I think this is OK? So far, everything actually works, as much of a hack as it seems like it may be. It's important to note that if I try to run that code on the UI thread, it locks, because it waits on the WaitOne() forever, locking the thread, so it can't make the Load request to the server. So once the data is displayed, users can click on one as it goes by to fill a details pane with the full DataB data about that object. To do that, I have the the details pane user control subscribing to a selection event I have setup, which gets fired when the selection changes (on the UI thread). I use a similar technique there, to get the DataB object: void SelectionService_SelectedDataAChanged(object sender, EventArgs e) { DataA dataA = /*Get the selected DataA*/; MyDomainContext context = new MyDomainContext(); var loadOperationGetDataB = context.Load(context.GetDataBQuery(dataA.DataAID), System.ServiceModel.DomainServices.Client.LoadBehavior.RefreshCurrent, false); loadOperationGetDataB.Completed += new EventHandler(loadOperationGetDataB_Completed); } private void loadOperationGetDataB_Completed(object sender, EventArgs e) { this.DataContext = ((LoadOperation<DataB>)sender).Entities.SingleOrDefault(); } Again, it seems kinda hacky, but it works... except on the DataB that it loads, the DataCs list is empty. I've tried all kinds of things there, and I don't see what I'm doing wrong to allow the DataCs to come down with the DataB. I'm about ready to make a 3rd query for the DataCs, but that's screaming even more hackiness to me. It really feels like I'm fighting against the grain here, like I'm doing this in an entirely unintended way. If anyone could offer any assistance, and point out what I'm doing wrong here, I'd very much appreciate it! Thanks!

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  • Best programming aids for a quadriplegic programmer

    - by Peter Rowell
    Before you jump to conclusions, yes, this is programming related. It covers a situation that comes under the heading of, "There, but for the grace of God, go you or I." This is brand new territory for me so I'm asking for some serious help here. A young man, Honza Ripa, in a nearby town did the classic Dumb Thing two weeks after graduating from High School -- he dove into shallow water in the Russian River and had a C-4/C-5 break, sometimes called a Swimming Pool break. In a matter of seconds he went from an exceptional golfer and wrestler to a quadriplegic. (Read the story ... all of us should have been so lucky as to have a girlfriend like Brianna.) That was 10 months ago and he has regained only tiny amounts of control of his right index finger and a couple of other hand/foot motions, none of them fine-grained. His total control of his computer (currently running Win7, but we can change that as needed) is via voice command. Honza's not dumb. He had a 3.7 GPA with AP math and physics. The Problems: Since all of his input is via voice command, he is concerned that the predominance of special characters in programming will require vast amount of verbose commands. Does anyone know of any well done voice input system specifically designed for programmers? I'm thinking about something that might be modal--e.g. you say "Python input" and it goes into a macro mode for doing class definitions, etc. Given all of the RSI in programmer-land there's got to be something out there. What OS(es) does it run on? I am planning on teaching him Python, which is my preferred language for programming and teaching. Are there any applications / whatevers that are written in Python and would be a particularly good match for engaging him mentally while supporting his disability? One of his expressed interests is in stock investing, but that not might be a good starting point for a brand-new programmer. There are a lot of environments (Flash, JavaScript, etc) that are not particularly friendly to people with accessibility challenges. I vaguely remember (but cannot find) a research project that basically created an overlay system on top of a screen environment and then allowed macro command construction on top of the screen image. If we can get/train this system, we may be able to remove many hurdles to using the net. I am particularly interested in finding open source Python-based robotics and robotic prostheses projects so that he can simultaneously learn advanced programming concepts while learning to solve some of his own immediate problems. I've done a ton of googling on this, but I know there things I'm missing. I'm asking the SO community to step up to the plate here. I know this group has the answers, so let me hear them! Overwhelm me with the opportunities that any of us might have/need to still program after such a life-changing event.

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  • Hypercom P2100 pinpad programming

    - by Xience
    Hey guys, i have got a Hypercom P2100 pinpad that i need to incorporate in my POS app. I tried to access it through hyperterminal but didn't succeed. It is connected to my machine through a USB to Serial interface, could that be the source of problem. In addition, upon googling the programming samples that i could find just showed, at max, reading data on serial port but nothing on programming the pinpad itself. Any help is greatly appreciated.

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  • Examples of Dynamics AX 2009 programming?

    - by Sam
    I'm just learning to program Dynamics AX 2009. So far I got the dev system running, I got some background about the architecture. Now I'm looking for some walkthrough-samples to learn more about programming in this system. Are there some samples available online? Can someone point me to some learning help? Maybe to some good AX-programming related blogs? How did you learn to program DAX9?

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  • Yii: Multi-language website - best practices.

    - by michal
    Hi, I find Yii great framework, and the example website created with yiic shell is a good point to start... however it doesn't cover the topic of multi-language websites, unfortunately. The docs covers the topic of translating short messages, but not keeping the multi-lingual content ... I'm about to start working on a website which needs to be in at least two languages, and I'm wondering what is the best way to keep content for that ... The problem is that the content is mixed extensively with common elements (like embedded video files). I need to avoid duplicating those commons ... so far I used to have an array of arrays containing texts (usually no more than 1-2 short paragraphs), then the view file was just rendering the text from an array. Now I'd like to avoid keeping it in arrays (which requires some attention when putting double quotations " " and is inconvenient in general...). So, what is the best way to keep those short paragraphs? Should I keep them in DB like (id | msg_id | language | content ) and then select them by msg_id & language? That still requires me to create some msg_id's and embed them into view file ... Is there any recommended paradigm for which Yii has some solutions? Thanks, m.

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  • Suggestions for programming language and database for a high end database querying system (>50 milli

    - by mmdave
    These requirements are sketchy at the moment, but will appreciate any insights. We are exploring what would be required to build a system that can handle 50 database million queries a day - specifiically from the programming language and database choice Its not a typical website, but an API / database accessing through the internet. Speed is critical. The application will primarily receive these inputs (about a few kb each) and will have to address each of them via the database lookup. Only a few kb will be returned. The server will be run over https/ssl.

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  • Which book for windows Shell programming?

    - by serefarikan
    I've been looking for a good book for windows shell programming, and the only one I could find is Visual C++ Windows Shell Programming by Dino Eposito: http://www.wintellect.com/BookInformation.aspx?ASIN=1861001843 It is an old book, and I'd like to know if you know of any good resources which could help. I need to develop a couple of windows explorer extensions, and apparently managed code is not recommended by Microsoft at least for some of these tasks. So I'm searching for a good resource for native development. Kind regards Seref

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  • Git branching / rebasing good practices

    - by Pawel Krupinski
    I have a following scenario: 3 branches: - Master - MyBranch branched off Master for the purpose of developing a new feature of the system - MyBranchLocal branched off MyBranch as my local copy of the branch MyBranch is being rebased against and pushed to by other developers (who are working on the same feature as I am). As the owner of the MyBranch branch I want to keep it in sync with Master by rebasing. I also need to merge the changes I make to MyBranchLocal with MyBranch. What is a good way to do that? Couple of possible scenarios I tried so far: I. 1. Commit change to MyBranchLocal 2. Rebase MyBranch against Master 3. Rebase MyBranchLocal against MyBranch 4. Merge MyBranch with MyBranchLocal II. 1. Commit change to MyBranchLocal 2. Merge MyBranch with MyBranchLocal 3. Rebase MyBranch against Master 4. Rebase MyBranchLocal against MyBranch III. 1. Commit change to MyBranchLocal 2. Rebase MyBranch against Master 3. Merge MyBranch with MyBranchLocal 4. Rebase MyBranchLocal against MyBranch I already know that scenario III seems to be messing the commit history up a lot, potentially duplicating commits. What is your experience? What scenarios do you recommend?

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  • Best practices for defining and initializing variables in web.xml and then accessing them from Java

    - by DutrowLLC
    I would like to define and initialize some variables in web.xml and the access the values of these variables inside my Java application. The reason I want to do this is because I would like to be able to change the values of these variables without having to recompile the code. What is the best practice for doing this? Most of the variables are just strings, maybe some numbers as well. Does the class that accesses the variables have to be a servlet? Thanks! Chris

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  • Examples for Apex Programming [ salesforce.com platform ]

    - by javatechi
    HI all, i m new to salesforce.com platform, also to Apex code development. I m creating an application in which i need to use Apex programming, and i have java development background. So what i need is, as many examples as possible in Apex programming [ salesforce.com ], so if anybody can provide me the websites which i can look into, so it will be helpful. Thank You

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  • Specialized course in Web programming or Generalized course in Computer Science?

    - by Sugan
    I am planning to do my masters in Computer Science in UK. I am interested in Web programming. What should I opt for. A general course in Computer Science or in some specialized course in Web Programming. If web programming, are there a lot of colleges offering these courses. Are there a lot of job offers there in UK. I am not sure whether I can ask this question here. If not point me where I can ask this question.

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  • Create XML File Using XML Schema

    - by metdos
    Is there any easy way to create at least a template XML file using XML Schema? My main interest is bounded by C++, but discussions of other programming languages are also welcome.By the way I also use QT framework.

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  • Best Practices for Sanitizing SQL inputs Using JavaScript?

    - by Greg Bulmash
    So, with HTML5 giving us local SQL databases on the client side, if you want to write a select or insert, you no longer have the ability to sanitize third party input by saying $buddski = mysql_real_escape_string($tuddski) because the PHP parser and MySQL bridge are far away. It's a whole new world of SQLite where you compose your queries and parse your results with JavaScript. But while you may not have your whole site's database go down, the user who gets his/her database corrupted or wiped due to a malicious injection attack is going to be rather upset. So, what's the best way, in pure JavaScript, to escape/sanitize your inputs so they will not wreak havoc with your user's built-in database? Scriptlets? specifications? Anyone?

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  • Partials vs for loop — best practices

    - by Mike
    In coding up your view templates you can render a partial and pass an array of objects to be rendered once per object. OR you can use a For blank in @blank loop. How do you decide when to do which? It seems that if you use a partial for every iterable object you will end up having to modify tons of separate files to make changes to potentially one view. With the loops you can see everything right there in one file.

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  • H.264 / FLV best practices for HTML

    - by Steve Murch
    I run a website with about 700 videos (And no, it's not porn -- get your mind out of the gutter :-) ). The videos are currently in FLV format. We use the JWPlayer to render those videos. IIS6 hosted. Everything works just fine. As I understand it, H.264 (not FLV and likely not OGG) is the emerging preferred HTML5 video standard. Today, the iPad really only respects H.264 or YouTube. Presumably, soon many more important browsers will follow Apple's lead and respect only the HTML5 tag. OK, so I think I can figure out how to convert my existing videos into the proper H.264 format. There are various tools available, including ffmpeg.exe. I haven't tried it yet, but I don't think that's going to be a problem after fiddling with the codec settings. My question is more about the container itself -- that is, planning graceful transition for all users. What's the best-practice recommendation for rendering these videos? If I just use the HTML5 tag, then presumably any browser that doesn't yet support HTML5 won't see the videos. And if I render them in Flash format via the JWPlayer or some other player, then they won't be playable on the iPad. Do I have to do ugly UserAgent detection here to figure out what to render? I know the JWPlayer supports H.264 media, but isn't the player itself a Flash component and therefore not playable on the iPad? Sorry if I'm not being clear, but I'm scratching my head on a graceful transition plan that will work for current browsers, the iPad and the upcoming HTML5 wave. I'm not a video expert, so any advice would be most welcome, thanks.

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  • Fluent API Style Usage

    - by Chris Dwyer
    When programming against a fluent API, I've seen the style mostly like this: var obj = objectFactory.CreateObject() .SetObjectParameter(paramName, value) .SetObjectParameter(paramName, value) .DoSomeTransformation(); What is the reasoning behind putting the dot at the beginning of the line instead of the end of the line like this: var obj = objectFactory.CreateObject(). SetObjectParameter(paramName, value). SetObjectParameter(paramName, value). DoSomeTransformation(); Or, is it merely a style thing that a team makes a consensus on?

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  • Whats the point of STL?

    - by Jonathan D
    I've been programming c++ for about a year now and when i'm looking about i see lots of references to STL. Can some one please tell me what it does? and the advantages and disadvantageous of it? thanks

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  • App.Config Best Practices ?

    - by abmv
    Normally when you have a application configuration file in your application and your application is expected to read from it. Is it good to check initially at start up if this file exists and raise an error and not to proceed at all ? (Worse case senarios) Or leave it to the unhandled exception manager to handle it and shut down the application? (WPF/Winforms etc)

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