Omar AL Zabir blog on ASP.NET Ajax and .NET 3.5

You must have noticed Microsoft’s new tool Doloto which helps solve the following problem:

Windows 7 64bit finally works! This is the first 64bit OS I could really use in my daily acitvities. I tried Vista 64bit, it was unreliable. It would show blue screen right when I am about to make a presentation to the CEO. Until Microsoft released SP1, Vista 64 bit was not usable at all. Then came Windows 7 beta. I immediately tried the 64bit version of Windows 7 beta. It was even worse than Vista. It would crash every now and then – waking up from standby, trying to do livemeeting share, switching screens, plugging in external USB drives and what not. So, I patiently waited for the final version to come out before I get on installing it on all my laptops. Happy to say, the final version works perfectly on HP tx2000 Tablet PC, DELL Vostro 1500, DELL Inspiron 1520. Once you do a full windows update and install some drivers here and there, it all works perfectly. And let me say, Windows 7 is beautiful. I found back the joy of working on computers again!

Aspects are common features that you write every now and then in different parts of your project. it can be some specific way of handling exceptions in your code, or logging method calls, or timing execution of methods, or retrying some methods and so on. If you are not doing it using any Aspect Oriented Programming framework, then you are repeating a lot of similar code throughout the project, which is making your code hard to maintain. For ex, say you have a business layer where methods need to be logged, errors need to be handled in a certain way, execution needs to be timed, database operations need to be retried and so on. So, you write code like this:

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Visual Studio 2008 comes with rich Web Testing support, but it’s not rich enough to test highly dynamic AJAX websites where the page content is generated dynamically from database and the same page output changes very frequently based on some external data source e.g. RSS feed. Although you can use the Web Test Record feature to record some browser actions by running a real browser and then play it back. But if the page that you are testing changes everytime you visit the page, then your recorded tests no longer work as expected. The problem with recorded Web Test is that it stores the generated ASP.NET Control ID, Form field names inside the test. If the page is no longer producing the same ASP.NET Control ID or same Form fields, then the recorded test no longer works. A very simple example is in VS Web Test, you can say “click the button with ID ctrl00_UpdatePanel003_SubmitButton002”, but you cannot say “click the 2nd Submit button inside the third UpdatePanel”. Another key limitation is in Web Tests, you cannot address Controls using the Server side Control ID like “SubmitButton”. You have to always use the generated Client ID which is something weird like “ctrl_00_SomeControl001_SubmitButton”. Moreover, if you are making AJAX calls where certain call returns some JSON or updates some UpdatePanel and then based on the server returned response, you want to make further AJAX calls or post the refreshed UpdatePanel, then recorded tests don’t work properly. You *do* have the option to write the tests hand coded and write code to handle such scenario but it’s pretty difficult to write hand coded tests when you are using UpdatePanels because you have to keep track of the page viewstates, form hidden variables etc across async post backs. So, I have built a library that makes it significantly easier to test dynamic AJAX websites and UpdatePanel rich web pages. There are several ExtractionRule and ValidationRule available in the library which makes testing Cookies, Response Headers, JSON output, discovering all UpdatePanel in a page, finding controls in the response body, finding controls inside some UpdatePanel all very easy.

Dropthings – my open source Web 2.0 Ajax Portal has gone through a technology overhauling. Previously it was built using ASP.NET AJAX, a little bit of Workflow Foundation and Linq to SQL. Now Dropthings boasts full jQuery front-end combined with ASP.NET AJAX UpdatePanel, Silverlight widget, full Workflow Foundation implementation on the business layer, 100% Linq to SQL Compiled Queries on the data access layer, Dependency Injection and Inversion of Control (IoC) using Microsoft Enterprise Library 4.1 and Unity. It also has a ASP.NET AJAX Web Test framework that makes it real easy to write Web Tests that simulates real user actions on AJAX web pages. This article will walk you through the challenges in getting these new technologies to work in an ASP.NET website and how performance, scalability, extensibility and maintainability has significantly improved by the new technologies. Dropthings has been licensed for commercial use by prominent companies including BT Business, Intel, Microsoft IS, Denmark Government portal for Citizens; Startups like Limead and many more. So, this is serious stuff! There’s a very cool open source implementation of Dropthings framework available at National University of Singapore portal.

Recently after Load Testing my open source project Dropthings, I encountered a lot of memory leak. I found lots of Workflow Instances and Linq Entities were left in memory and never collected. After profiling the web application using .NET Memory Profiler, it showed the real picture:

Last year at Pageflakes, when we were getting millions of hits per day, we were having query timeout due to lock timeout and Transaction Deadlock errors. These locks were produced from aspnet_Users and aspnet_Membership tables. Since both of these tables are very high read (almost every request causes a read on these tables) and high write (every anonymous visit creates a row on aspnet_Users), there were just way too many locks created on these tables per second. SQL Counters showed thousands of locks per second being created. Moreover, we had queries that would select thousands of rows from these tables frequently and thus produced more locks for longer period, forcing other queries to timeout and thus throw errors on the website.