Archives
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Strongly typed workflow input and output arguments
When you run a Workflow using Workflow Foundation, you pass arguments to the workflow in a Dictionary form where the type of Dictionary is Dictionary<string, object>. This means you miss the strong typing features of .NET languages. You have to know what arguments the workflow expects by looking at the Workflow public properties. Moreover, there’s no way to make arguments required. You pass parameter, expect it to run, if it throws exception, you pass more arguments, hope it works now. Similarly, if you are running workflow synchronously using ManualWorkflowSchedulerService, you expect return arguments from the Workflow immediately, but there again, you have to rely on the Dictionary key and value pair. No strong typing there as well.
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99.99% available ASP.NET and SQL Server Production Architecture for SaaS
You have a hot ASP.NET+SQL Server product, growing at thousand users per day and you have hit the limit of your own garage hosting capability. Now that you have enough VC money in your pocket, you are planning to go out and host on some real hosting facility, maybe a colocation or managed hosting. So, you are thinking, how to design a physical architecture that will ensure performance, scalability, security and availability of your product? How can you achieve four-nine (99.99%) availability? How do you securely let your development team connect to production servers? How do you choose the right hardware for web and database server? Should you use Storage Area Network (SAN) or just local disks on RAID? How do you securely connect your office computers to production environment?
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Linq to SQL: Delete an entity using Primary Key only
Linq to Sql does not come with a function like .Delete(ID) which allows you to delete an entity using it’s primary key. You have to first get the object that you want to delete and then call .DeleteOnSubmit(obj) to queue it for delete. Then you have to call DataContext.SubmitChanges() to play the delete queries on database. So, how to delete object without getting them from database and avoid database roundtrip?
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Solving common problems with Compiled Queries in Linq to Sql for high demand ASP.NET websites
If you are using Linq to SQL, instead of writing regular Linq Queries, you should be using Compiled Queries. if you are building an ASP.NET web application that’s going to get thousands of hits per hour, the execution overhead of Linq queries is going to consume too much CPU and make your site slow. There’s a runtime cost associated with each and every Linq Query you write. The queries are parsed and converted to a nice SQL Statement on *every* hit. It’s not done at compile time because there’s no way to figure out what you might be sending as the parameters in the queries during runtime. So, if you have common Linq to Sql statements like the following one throughout your growing web application, you are soon going to have scalability nightmares:
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How to convince developers and management to use automated unit test for AJAX websites
Everyone agrees that unit testing is a good thing, we should all write unit tests. We read articles and blogs to keep us up-to-date on what’s going on in the unit test world so that we can sound cool talking to peers at lunch. But when we really sit down and try to write unit tests ourselves – “Naaah, this is waste of time, let’s ask my QA to test it; that’s much more reliable and guaranteed way to test this. What’s the point testing these functions when there are so many other functions that we should unit test first?” Had such moment yourself or with someone else? Read on.
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Tips and tricks to rescue overdue projects
One of my friends, who runs his own offshore development shop, was having nightmare situation with one of his customers. He's way overdue on a release, the customer is screaming everyday, he's paying his team from his own pocket, customer is sending an ever increasing list of changes and so on. Here's how we discussed some ideas to get out of such a situation and make sure it does not repeat in future:
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An Agile Developer's workflow when SCRUM is used
If you are planning to start SCRUM at your company, you might need to train developers and QA to get into the mindset of an Agile developer. SCRUM is only successful when the developers and QA get into the habit of following the principles of SCRUM by heart. So, sometimes you need to offer training or do trial sprints to give some room to your developers how to get used to the working fashion of SCRUM. Giving them a handy workflow diagram that shows how they should work helps soothe the steep learning curve required for non-super star developers. I made such a workflow while I was teaching SCRUM at my friend's company. The following diagram was printed and hung over the desk of each and every developer to help them grasp the culture of SCRUM quickly:
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ASP.NET website Continuous Integration+Deployment using CruiseControl.NET, Subversion, MSBuild and Robocopy
You can setup continuous integration and automated deployment for your web application using CruiseControl.NET, Subversion, MSBuild and Robocopy. I will show you how you can automatically build the entire solution, email build report to developers and QA, deploy latest code in IIS all using CruiseControl.NET every N minutes.
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Using multiple broadband connections without using any special router or software
I have two broadband connections. One cheap connection, which I mostly use for browsing and downloading. Another very expensive connection that I use for voice chat, remote desktop connection etc. Now, using these two connections at the same time required two computers before. But I figured out a way to use both connections at the same time using the same computer. Here's how:
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Best practices for creating websites in IIS 6.0
Every time I create an IIS website, I do some steps, which I consider as best practice for creating any IIS website for better performance, maintainability, and scalability. Here' re the things I do:
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Create ASP.NET MVC Controllers under Namespace and specific URL
When you have a lot of controllers, you need to organize them under Namespaces. Also, it is better to put controllers under subfolders in order to organize them properly and have some meaningful URL for them like /Admin/User where Admin is the subfolder and User is the controller. For example, you might have a lot of controllers that are APIs exposed by your web app, not regular pages. So, you might want to put them under /API/ folder. You also want to make sure no one can access those controllers from the root url. For example, no one must call /User/GetUserList instead they must call /API/User/GetUserList
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Create REST API using ASP.NET MVC that speaks both Json and plain Xml
ASP.NET MVC Controllers can directly return objects and collections, without rendering a view, which makes it quite appealing for creating REST like API. The nice extensionless Url provided by MVC makes it handy to build REST services, which means you can create APIs with smart Url like "something.com/API/User/GetUserList"
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HTTP handler to combine multiple files, cache and deliver compressed output for faster page load
It's a good practice to use many small Javascript and CSS files instead of one large Javascript/CSS file for better code maintainability, but bad in terms of website performance. Although you should write your Javascript code in small files and break large CSS files into small chunks but when browser requests those javascript and css files, it makes one Http request per file. Every Http Request results in a network roundtrip form your browser to the server and the delay in reaching the server and coming back to the browser is called latency. So, if you have four javascripts and three css files loaded by a page, you are wasting time in seven network roundtrips. Within USA, latency is average 70ms. So, you waste 7x70 = 490ms, about half a second of delay. Outside USA, average latency is around 200ms. So, that means 1400ms of waiting. Browser cannot show the page properly until Css and Javascripts are fully loaded. So, the more latency you have, the slower page loads.
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Loading static content in ASP.NET pages from different domain for faster parallel download
Generally we put static content (images, css, js) of our website inside the same web project. Thus they get downloaded from the same domain like www.dropthings.com. There are three problems in this approach:
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Open Source ASP.NET 3.5 AJAX Portal - new and improved
Last week I released a new version of Dropthings, my open source AJAX portal, that shows many fancy Web 2.0 features and showcases extensive use of ASP.NET 3.5, Workflow Foundation, C# 3.0 new language features, custom ASP.NET AJAX extenders, many performance and scalability techniques. I have written a book on these topics as well.
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Deploy ASP.NET MVC on IIS 6, solve 404, compression and performance problems
There are several problems with ASP.NET MVC application when deployed on IIS 6.0:
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ensure - Ensure relevant Javascript and HTML are loaded before using them
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UFrame: goodness of UpdatePanel and IFRAME combined
UFrame combines the goodness of UpdatePanel and IFRAME in a cross browser and cross platform solution. It allows a DIV to behave like an IFRAME loading content from any page either static or dynamic. It can load pages having both inline and external Javascript and CSS, just like an IFRAME. But unlike IFRAME, it loads the content within the main document and you can put any number of UFrame on your page without slowing down the browser. It supports ASP.NET postback nicely and you can have DataGrid or any other complex ASP.NET control within a UFrame. UFrame works perfectly with ASP.NET MVC making it an replacement for UpdatePanel. Best of all, UFrame is implemented 100% in Javascript making it a cross platform solution. As a result, you can use UFrame on ASP.NET, PHP, JSP or any other platform.
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Fast ASP.NET web page loading by downloading multiple javascripts in batch
A web page can load a lot faster and feel faster if the javascripts on the page can be loaded after the visible content has been loaded and multiple javascripts can be batched into one download. Browsers download one external script at a time and sometimes pause rendering while a script is being downloaded and executed. This makes web pages load and render slow when there are multiple javascripts on the page. For every javascript reference, browser stops downloading and processing of any other content on the page and some browsers (like IE6) pause rendering while it processes the javascript. This gives a slow loading experience and the web page kind of gets 'stuck' frequently. As a result, a web page can only load fast when there are small number of external scripts on the page and the scripts are loaded after the visible content of the page has loaded.
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Fast, Streaming AJAX proxy - continuously download from cross domain
Due to browser's prohibition on cross domain XMLHTTP call, all AJAX websites must have server side proxy to fetch content from external domain like Flickr or Digg. From client side javascript code, an XMLHTTP call goes to the server side proxy hosted on the same domain and then the proxy downloads the content from the external server and sends back to the browser. In general, all AJAX websites on the Internet that are showing content from external domains are following this proxy approach except some rare ones who are using JSONP. Such a proxy gets a very large number of hits when a lot of component on the website are downloading content from external domains. So, it becomes a scalability issue when the proxy starts getting millions of hits. Moreover, web page's overall load performance largely depends on the performance of the proxy as it delivers content to the page. In this article, we will take a look how we can take a conventional AJAX Proxy and make it faster, asynchronous, continuously stream content and thus make it more scalable.
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Reduce website download time by heavily compressing PNG and JPEG
PNG and JPEG are two most popular formats for web graphics. JPEG is used for photographs, screenshots and backgrounds where PNG is used for all other graphics need including cliparts, buttons, headers, footers, borders and so on. As a result, these two types of graphics file usually take up 80% of the total graphics used in a website. Of course, there's the GIF, which is very popular. But as it supports only 256 colors, it is losing its popularity day by day. PNG seems to be a all rounder winner for all kinds of graphics need. As all browsers support PNG well enough and PNG supports alpha transparency, it's surely the best format so far on the web for all purpose graphics need for websites. So, if you can optimize all PNG and JPEG on your website and compress them rigorously, you can easily shed off several seconds of load time from your website without doing any coding. Especially if your website is graphics rich like Pageflakes, 30% reduction in total size of graphics throughout the website is a big performance win.
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Fast page loading by moving ASP.NET AJAX scripts after visible content
ASP.NET ScriptManager control has a property LoadScriptsBeforeUI, when set to false, should load all AJAX framework scripts after the content of the page. But it does not effectively push down all scripts after the content. Some framework scripts, extender scripts and other scripts registered by Ajax Control Toolkit still load before the page content loads. The following screen taken from www.dropthings.com shows several script tags are still added at the beginning of <form> which forces them to download first before the page content is loaded and displayed on the page. Script tags pause rendering on several browsers especially in IE until the scripts download and execute. As a result, it gives user a slow loading impression as user stares at a white screen for some time until the scripts before the content download and execute completely. If browser could render the html before it downloads any script, user would see the page content immediately after visiting the site and not see a white screen. This will give user an impression that the website is blazingly fast (just like Google homepage) because user will ideally see the page content, if it's not too large, immediately after hitting the URL.
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HTML and IFRAME widget for Dropthings
I made two new widgets for Dropthings - one is an HTML widget, that allows you to put any HTML content inside a widget and the other one is an IFRAME widget that allows you to host an IFRAME to any URL. You can see example of these widgets from www.dropthings.com.
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Desktop RSS Feed Aggregator client with Outlook Integration
Back in 2005, I built an open source RSS Feed Aggregator Desktop client which has been quite popular since its release. It has 48,672 downloads so far. From the activity I see on sourceforge statistics, it's being used about 20,000 times per day.
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10 ASP.NET Performance and Scalability Secrets
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My first book - Building a Web 2.0 Portal with ASP.NET 3.5
My first book "Building a Web 2.0 Portal with ASP.NET 3.5" from O'Reilly is published and available in the stores. This book explains in detail the architecture design, development, test, deployment, performance and scalability challenges of my open source web portal http://dropthings.omaralzabir.com. Dropthings is a prototype of a web portal similar to iGoogle or Pageflakes. But this portal is developed using recently released brand new technologies like ASP.NET 3.5, C# 3.0, Linq to Sql, Linq to XML, and Windows Workflow foundation. It makes heavy use of ASP.NET AJAX 1.0. Throughout my career I have built several state-of-the-art personal, educational, enterprise and mass consumer web portals. This book collects my experience in building all of those portals.