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  • Do not use “using” in WCF Client

    - by oazabir
    You know that any IDisposable object must be disposed using using. So, you have been using using to wrap WCF service’s ChannelFactory and Clients like this: using(var client = new SomeClient()) {. ..} Or, if you are doing it the hard and slow way (without really knowing why), then: using(var factory = new ChannelFactory<ISomeService>()) {var channel= factory.CreateChannel();...} That’s what we have all learnt in school right? We have learnt it wrong! When there’s a network related error or the connection is broken, or the call is timed out before Dispose is called by the using keyword, then it results in the following exception when the using keyword tries to dispose the channel: failed: System.ServiceModel.CommunicationObjectFaultedException : The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state. Server stack trace: at System.ServiceModel.Channels.CommunicationObject.Close(TimeSpan timeout) Exception rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) at System.ServiceModel.ICommunicationObject.Close(TimeSpan timeout) at System.ServiceModel.ClientBase`1.System.ServiceModel.ICommunicationObject.Close(TimeSpan timeout) at System.ServiceModel.ClientBase`1.Close() at System.ServiceModel.ClientBase`1.System.IDisposable.Dispose() There are various reasons for which the underlying connection can be at broken state before the using block is completed and the .Dispose() is called. Common problems like network connection dropping, IIS doing an app pool recycle at that moment, some proxy sitting between you and the service dropping the connection for various reasons and so on. The point is, it might seem like a corner case, but it’s a likely corner case. If you are building a highly available client, you need to treat this properly before you go-live. So, do NOT use using on WCF Channel/Client/ChannelFactory. Instead you need to use an alternative. Here’s what you can do: First create an extension method. public static class WcfExtensions{ public static void Using<T>(this T client, Action<T> work) where T : ICommunicationObject { try { work(client); client.Close(); } catch (CommunicationException e) { client.Abort(); } catch (TimeoutException e) { client.Abort(); } catch (Exception e) { client.Abort(); throw; } }} Then use this instead of the using keyword: new SomeClient().Using(channel => { channel.Login(username, password);}); Or if you are using ChannelFactory then: new ChannelFactory<ISomeService>().Using(channel => { channel.Login(username, password);}); Enjoy!

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  • Open Source WPF UML Design tool

    - by oazabir
    PlantUmlEditor is my new free open source UML designer project built using WPF and .NET 3.5. If you have used plantuml before, you know that you can quickly create sophisitcated UML diagrams without struggling with a designer. Especially those who use Visio to draw UML diagrams (God forbid!), you will be at heaven. This is a super fast way to get your diagrams up and ready for show. You can *write* UML diagrams in plain English, following a simple syntax and get diagrams generated on-the-fly. This editor really saves time designing UML diagrams. I have to produce quick diagrams to convey ideas quickly to Architects, Designers and Developers everyday. So, I use this tool to write some quick diagrams at the speed of coding, and the diagrams get generated on the fly. Instead of writing a long mail explaining some complex operation or some business process in English, I can quickly write it in the editor in almost plain English, and get a nice looking activity/sequence diagram generated instantly. Making major changes is also as easy as doing search-replace and copy-pasting blocks here and there. You don't get such agility in any conventional mouse-based UML designers. I have submited a full codeproject article to give you a detail walkthrough how I have built this. Please read this article and vote for me if you like it. PlantUML Editor: A fast and simple UML editor using WPF http://www.codeproject.com/KB/smart/plantumleditor.aspx You can download the project from here: http://code.google.com/p/plantumleditor/

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  • ParallelWork: Feature rich multithreaded fluent task execution library for WPF

    - by oazabir
    ParallelWork is an open source free helper class that lets you run multiple work in parallel threads, get success, failure and progress update on the WPF UI thread, wait for work to complete, abort all work (in case of shutdown), queue work to run after certain time, chain parallel work one after another. It’s more convenient than using .NET’s BackgroundWorker because you don’t have to declare one component per work, nor do you need to declare event handlers to receive notification and carry additional data through private variables. You can safely pass objects produced from different thread to the success callback. Moreover, you can wait for work to complete before you do certain operation and you can abort all parallel work while they are in-flight. If you are building highly responsive WPF UI where you have to carry out multiple job in parallel yet want full control over those parallel jobs completion and cancellation, then the ParallelWork library is the right solution for you. I am using the ParallelWork library in my PlantUmlEditor project, which is a free open source UML editor built on WPF. You can see some realistic use of the ParallelWork library there. Moreover, the test project comes with 400 lines of Behavior Driven Development flavored tests, that confirms it really does what it says it does. The source code of the library is part of the “Utilities” project in PlantUmlEditor source code hosted at Google Code. The library comes in two flavors, one is the ParallelWork static class, which has a collection of static methods that you can call. Another is the Start class, which is a fluent wrapper over the ParallelWork class to make it more readable and aesthetically pleasing code. ParallelWork allows you to start work immediately on separate thread or you can queue a work to start after some duration. You can start an immediate work in a new thread using the following methods: void StartNow(Action doWork, Action onComplete) void StartNow(Action doWork, Action onComplete, Action<Exception> failed) For example, ParallelWork.StartNow(() => { workStartedAt = DateTime.Now; Thread.Sleep(howLongWorkTakes); }, () => { workEndedAt = DateTime.Now; }); Or you can use the fluent way Start.Work: Start.Work(() => { workStartedAt = DateTime.Now; Thread.Sleep(howLongWorkTakes); }) .OnComplete(() => { workCompletedAt = DateTime.Now; }) .Run(); Besides simple execution of work on a parallel thread, you can have the parallel thread produce some object and then pass it to the success callback by using these overloads: void StartNow<T>(Func<T> doWork, Action<T> onComplete) void StartNow<T>(Func<T> doWork, Action<T> onComplete, Action<Exception> fail) For example, ParallelWork.StartNow<Dictionary<string, string>>( () => { test = new Dictionary<string,string>(); test.Add("test", "test"); return test; }, (result) => { Assert.True(result.ContainsKey("test")); }); Or, the fluent way: Start<Dictionary<string, string>>.Work(() => { test = new Dictionary<string, string>(); test.Add("test", "test"); return test; }) .OnComplete((result) => { Assert.True(result.ContainsKey("test")); }) .Run(); You can also start a work to happen after some time using these methods: DispatcherTimer StartAfter(Action onComplete, TimeSpan duration) DispatcherTimer StartAfter(Action doWork,Action onComplete,TimeSpan duration) You can use this to perform some timed operation on the UI thread, as well as perform some operation in separate thread after some time. ParallelWork.StartAfter( () => { workStartedAt = DateTime.Now; Thread.Sleep(howLongWorkTakes); }, () => { workCompletedAt = DateTime.Now; }, waitDuration); Or, the fluent way: Start.Work(() => { workStartedAt = DateTime.Now; Thread.Sleep(howLongWorkTakes); }) .OnComplete(() => { workCompletedAt = DateTime.Now; }) .RunAfter(waitDuration);   There are several overloads of these functions to have a exception callback for handling exceptions or get progress update from background thread while work is in progress. For example, I use it in my PlantUmlEditor to perform background update of the application. // Check if there's a newer version of the app Start<bool>.Work(() => { return UpdateChecker.HasUpdate(Settings.Default.DownloadUrl); }) .OnComplete((hasUpdate) => { if (hasUpdate) { if (MessageBox.Show(Window.GetWindow(me), "There's a newer version available. Do you want to download and install?", "New version available", MessageBoxButton.YesNo, MessageBoxImage.Information) == MessageBoxResult.Yes) { ParallelWork.StartNow(() => { var tempPath = System.IO.Path.Combine( Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), Settings.Default.SetupExeName); UpdateChecker.DownloadLatestUpdate(Settings.Default.DownloadUrl, tempPath); }, () => { }, (x) => { MessageBox.Show(Window.GetWindow(me), "Download failed. When you run next time, it will try downloading again.", "Download failed", MessageBoxButton.OK, MessageBoxImage.Warning); }); } } }) .OnException((x) => { MessageBox.Show(Window.GetWindow(me), x.Message, "Download failed", MessageBoxButton.OK, MessageBoxImage.Exclamation); }); The above code shows you how to get exception callbacks on the UI thread so that you can take necessary actions on the UI. Moreover, it shows how you can chain two parallel works to happen one after another. Sometimes you want to do some parallel work when user does some activity on the UI. For example, you might want to save file in an editor while user is typing every 10 second. In such case, you need to make sure you don’t start another parallel work every 10 seconds while a work is already queued. You need to make sure you start a new work only when there’s no other background work going on. Here’s how you can do it: private void ContentEditor_TextChanged(object sender, EventArgs e) { if (!ParallelWork.IsAnyWorkRunning()) { ParallelWork.StartAfter(SaveAndRefreshDiagram, TimeSpan.FromSeconds(10)); } } If you want to shutdown your application and want to make sure no parallel work is going on, then you can call the StopAll() method. ParallelWork.StopAll(); If you want to wait for parallel works to complete without a timeout, then you can call the WaitForAllWork(TimeSpan timeout). It will block the current thread until the all parallel work completes or the timeout period elapses. result = ParallelWork.WaitForAllWork(TimeSpan.FromSeconds(1)); The result is true, if all parallel work completed. If it’s false, then the timeout period elapsed and all parallel work did not complete. For details how this library is built and how it works, please read the following codeproject article: ParallelWork: Feature rich multithreaded fluent task execution library for WPF http://www.codeproject.com/KB/WPF/parallelwork.aspx If you like the article, please vote for me.

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  • Keep website and webservices warm with zero coding

    - by oazabir
    If you want to keep your websites or webservices warm and save user from seeing the long warm up time after an application pool recycle, or IIS restart or new code deployment or even windows restart, you can use the tinyget command line tool, that comes with IIS Resource Kit, to hit the site and services and keep them warm. Here’s how: First get tinyget from here. Download and install the IIS 6.0 Resource Kit on some PC. Then copy the tinyget.exe from “c:\program files…\IIS 6.0 ResourceKit\Tools'\tinyget” to the server where your IIS 6.0 or IIS 7 is running. Then create a batch file that will hit the pages and webservices. Something like this: SET TINYGET=C:\Program Files (x86)\IIS Resources\TinyGet\tinyget.exe"%TINYGET%" -srv:dropthings.omaralzabir.com -uri:http://dropthings.omaralzabir.com/ -status:200"%TINYGET%" -srv:dropthings.omaralzabir.com -uri:http://dropthings.omaralzabir.com/WidgetService.asmx?WSDL - status:200 First I am hitting the homepage to keep the webpage warm. Then I am hitting the webservice URL with ?WSDL parameter, which allows ASP.NET to compile the service if not already compiled and walk through all the operations and reflect on them and thus loading all related DLLs into memory and reducing the warmup time when hit. Tinyget gets the servers name or IP in the –srv parameter and then the actual URI in the –uri. I have specified what’s the HTTP response code to expect in –status parameter. It ensures the site is alive and is returning http 200 code. Besides just warming up a site, you can do some load test on the site. Tinyget can run in multiple threads and run loops to hit some URL. You can literally blow up a site with commands like this: "%TINYGET%" -threads:30 -loop:100 -srv:google.com -uri:http://www.google.com/ -status:200 Tinyget is also pretty useful to run automated tests. You can record http posts in a text file and then use it to make http posts to some page. Then you can put matching clause to check for certain string in the output to ensure the correct response is given. Thus with some simple command line commands, you can warm up, do some transactions, validate the site is giving off correct response as well as run a load test to ensure the server performing well. Very cheap way to get a lot done.

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  • Munq is for web, Unity is for Enterprise

    - by oazabir
    The Unity Application Block (Unity) is a lightweight extensible dependency injection container with support for constructor, property, and method call injection. It’s a great library for facilitating Inversion of Control and the recent version supports AOP as well. However, when it comes to performance, it’s CPU hungry. In fact it’s so CPU hungry that it makes it impossible to make it work at Internet Scale. I was investigating some CPU issue on a portal that gets around 3MM hits per day and I found unusually high CPU. Here’s why: I did some CPU profiling on my open source project Dropthings and found that the highest CPU is consumed by Unity’s Resolve<>(). There’s no funky use of Unity in the project. Straightforward Register<>() and Resolve<>(). But as you can see, Resolve<>() is consuming significantly high CPU even after the site is warm and has been running for a while. Then I tried Munq, which is a basic Dependency Injection Container. It has everything you will usually need in a regular project. It boasts to be the fastest DI out there. So, I converted all Unity code to Munq in Dropthings and did a CPU profile and Whala!   There’s no trace of any Munq calls anywhere. That proves Munq is a lot faster than Unity.

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  • Rescue overdue offshore projects and convince management to use automated tests

    - by oazabir
    I have published two articles on codeproject recently. One is a story where an offshore project was two months overdue, my friend who runs it was paying the team from his own pocket and he was drowning in ever increasing number of change requests and how we brainstormed together to come out of that situation. Tips and Tricks to rescue overdue projects Next one is about convincing management to go for automated test and give developers extra time per sprint, at the cost of reduced productivity for couple of sprints. It’s hard to negotiate this with even dev leads, let alone managers. Whenever you tell them - there’s going to be less features/bug fixes delivered for next 3 or 4 sprints because we want to automate the tests and reduce manual QA effort; everyone gets furious and kicks you out of the meeting. Especially in a startup where every sprint is jam packed with new features and priority bug fixes to satisfy various stakeholders, including the VCs, it’s very hard to communicate the benefits of automated tests across the board. Let me tell you of a story of one of my startups where I had the pleasure to argue on this and came out victorious. How to convince developers and management to use automated test instead of manual test If you like these, please vote for me!

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  • Quick ways to boost performance and scalability of ASP.NET, WCF and Desktop Clients

    - by oazabir
    There are some simple configuration changes that you can make on machine.config and IIS to give your web applications significant performance boost. These are simple harmless changes but makes a lot of difference in terms of scalability. By tweaking system.net changes, you can increase the number of parallel calls that can be made from the services hosted on your servers as well as on desktop computers and thus increase scalability. By changing WCF throttling config you can increase number of simultaneous calls WCF can accept and thus make most use of your hardware power. By changing ASP.NET process model, you can increase number of concurrent requests that can be served by your website. And finally by turning on IIS caching and dynamic compression, you can dramatically increase the page download speed on browsers and and overall responsiveness of your applications. Read the CodeProject article for more details. http://www.codeproject.com/KB/webservices/quickwins.aspx Please vote for me if you find the article useful.

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  • C# with keyword equivalent

    - by oazabir
    There’s no with keyword in C#, like Visual Basic. So you end up writing code like this: this.StatusProgressBar.IsIndeterminate = false; this.StatusProgressBar.Visibility = Visibility.Visible; this.StatusProgressBar.Minimum = 0; this.StatusProgressBar.Maximum = 100; this.StatusProgressBar.Value = percentage; Here’s a work around to this: With.A<ProgressBar>(this.StatusProgressBar, (p) => { p.IsIndeterminate = false; p.Visibility = Visibility.Visible; p.Minimum = 0; p.Maximum = 100; p.Value = percentage; }); Saves you repeatedly typing the same class instance or control name over and over again. It also makes code more readable since it clearly says that you are working with a progress bar control within the block. It you are setting properties of several controls one after another, it’s easier to read such code this way since you will have dedicated block for each control. It’s a very simple one line function that does it: public static class With { public static void A<T>(T item, Action<T> work) { work(item); } } You could argue that you can just do this: var p = this.StatusProgressBar; p.IsIndeterminate = false; p.Visibility = Visibility.Visible; p.Minimum = 0; p.Maximum = 100; p.Value = percentage; But it’s not elegant. You are introducing a variable “p” in the local scope of the whole function. This goes against naming conventions. Morever, you can’t limit the scope of “p” within a certain place in the function.

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  • Step by Step screencasts to do Behavior Driven Development on WCF and UI using xUnit

    - by oazabir
    I am trying to encourage my team to get into Behavior Driven Development (BDD). So, I made two quick video tutorials to show how BDD can be done from early requirement collection stage to late integration tests. It explains breaking user stories into behaviors, and then developers and test engineers taking the behavior specs and writing a WCF service and unit test for it, in parallel, and then eventually integrating the WCF service and doing the integration tests. It introduces how mocking is done using the Moq library. Moreover, it shows a way how you can write test once and do both unit and integration tests at the flip of a config setting. Watch the screencast here: Doing BDD with xUnit, Subspec and on a WCF Service  Warning: you might hear some noise in the audio in some places. Something wrong with audio bit rate. I suggest you let the video download for a while and then play it. If you still get noise, go back couple of seconds earlier and then resume play. It eliminates the noise.  The next video tutorial is about doing BDD to do automated UI tests. It shows how test engineers can take behaviors and then write tests that tests a prototype UI in isolation (just like Service Contract) in order to ensure the prototype conforms to the expected behaviors, while developers can write the real code and build the real product in parallel. When the real stuff is done, the same test can test the real stuff and ensure the agreed behaviors are satisfied. I have used WatiN to automate UI and test UI for expected behaviors. Doing BDD with xUnit and WatiN on a ASP.NET webform Hope you like it!

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  • Safely deploying changes to production servers

    - by oazabir
    When you deploy incremental changes on a production server, which is running and live all the time, you some times see error messages like “Compiler Error Message: The Type ‘XXX’ exists in both…”. Sometimes you find Application_Start event not firing although you shipped a new class, dll or web.config. Sometimes you find static variables not getting initialized and so on. There are so many weird things happen on webservers when you incrementally deploy changes to the server and the server has been up and running for several weeks. So, I came up with a full proof house keeping steps that we always do whenever we deploy some incremental change to our websites. These steps ensure that the web sites are properly recycled , cached are cleared, all the data stored at Application level is initialized. First of all you should have multiple web servers behind load balancer. This way you can take one server our of the production traffic, do your deployment and house keeping tasks like restarting IIS, and then put it back. Then you can do it for the second server and so on. This ensures there’s no outage for customer. If you can do it reasonable fast, hopefully customers won’t notice discrepancy between the servers some having new code and some having old code. You should only do this when your changes aren’t drastic. For ex, you aren’t delivering a complete revamped UI. In that case, some users hitting server1 with latest UI will suddenly get a completely different experience and then on next page refresh, they might hit server2 with old code and get a totally different experience. This works for incremental non-dramatic changes only.   During deployment you should follow these steps: Take server X out of load balancer so that it does not get any traffic. Stop all windows services on the server. Stop IIS. Delete the Temporary ASP.NET folders of all .NET versions incase you have multiple .NET versions running. You can follow this link. Deploy the changes. Flush any distributed cache you have, for ex, Velocity or Memcached. Start IIS. Start the windows services on the server. Warm up all websites by hitting major URLs on the websites. You should have some automated script to do this. You can use tinyget to hit some major URLs, especially pages that take a lot of time to compile. Read my post on keeping websites warm with zero coding. Put server X back to load balancer so that it starts receiving traffic. That’s it. It should give you a clean deployment and prevent unexpected errors. You should print these steps and hang on the desk of your deployment guys so that they never forget during deployment pressure.

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  • Caching WCF javascript proxy on browser

    - by oazabir
    When you use WCF services from Javascript, you have to generate the Javascript proxies by hitting the Service.svc/js. If you have five WCF services, then it means five javascripts to download. As browsers download javascripts synchronously, one after another, it adds latency to page load and slows down page rendering performance. Moreover, the same WCF service proxy is downloaded from every page, because the generated javascript file is not cached on browser. Here is a solution that will ensure the generated Javascript proxies are cached on browser and when there is a hit on the service, it will respond with HTTP 304 if the Service.svc file has not changed. Here’s a Fiddler trace of a page that uses two WCF services. You can see there are two /js hits and they are sequential. Every visit to the same page, even with the same browser session results in making those two hits to /js. Second time when the same page is browsed: You can see everything else is cached, except the WCF javascript proxies. They are never cached because the WCF javascript proxy generator does not produce the necessary caching headers to cache the files on browser. Here’s an HttpModule for IIS and IIS Express which will intercept calls to WCF service proxy. It first checks if the service is changed since the cached version on the browser. If it has not changed then it will return HTTP 304 and not go through the service proxy generation process. Thus it saves some CPU on server. But if the request is for the first time and there’s no cached copy on browser, it will deliver the proxy and also emit the proper cache headers to cache the response on browser. http://www.codeproject.com/Articles/360437/Caching-WCF-javascript-proxy-on-browser Don’t forget to vote.

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  • Finally! Entity Framework working in fully disconnected N-tier web app

    - by oazabir
    Entity Framework was supposed to solve the problem of Linq to SQL, which requires endless hacks to make it work in n-tier world. Not only did Entity Framework solve none of the L2S problems, but also it made it even more difficult to use and hack it for n-tier scenarios. It’s somehow half way between a fully disconnected ORM and a fully connected ORM like Linq to SQL. Some useful features of Linq to SQL are gone – like automatic deferred loading. If you try to do simple select with join, insert, update, delete in a disconnected architecture, you will realize not only you need to make fundamental changes from the top layer to the very bottom layer, but also endless hacks in basic CRUD operations. I will show you in this article how I have  added custom CRUD functions on top of EF’s ObjectContext to make it finally work well in a fully disconnected N-tier web application (my open source Web 2.0 AJAX portal – Dropthings) and how I have produced a 100% unit testable fully n-tier compliant data access layerfollowing the repository pattern. http://www.codeproject.com/KB/linq/ef.aspx In .NET 4.0, most of the problems are solved, but not all. So, you should read this article even if you are coding in .NET 4.0. Moreover, there’s enough insight here to help you troubleshoot EF related problems. You might think “Why bother using EF when Linq to SQL is doing good enough for me.” Linq to SQL is not going to get any innovation from Microsoft anymore. Entity Framework is the future of persistence layer in .NET framework. All the innovations are happening in EF world only, which is frustrating. There’s a big jump on EF 4.0. So, you should plan to migrate your L2S projects to EF soon.

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