Speed Optimization in ASP.NET 2.0 Web Applications - Part 2

Summary

In part 1 of this tutorial we mentioned five areas under which we can classify the techniques that can be used to optimize web application performance. In part 1 we explained the fist two areas only. Here we are going to cover the following remaining 3 sections:

- Page and server controls
- Web applications
- Coding practices

Page and Server Controls

The following topics give you an idea about how to use pages and controls efficiently in your web application:

Use HTML controls whenever possible

HTML controls is lighter than server controls especially if you are using server controls with its default properties. Server controls generally is easier to use than HTML controls, and on the other side they are slower than HTML controls. So, it is recommended to use HTML controls whenever possible and avoid using unnecessary server controls.

Avoid round trips to server whenever possible

Using server controls will extensively increase round trips to the server via their post back events which wastes a lot of time. You typically need to avoid these unnecessary round trips or post back events as possible. For example, validating user inputs can always (or at least in most cases) take place in the client side. There is no need to send these inputs to the server to check their validity. In general you should avoid code that causes a round trip to the server.

The Page.IsPostBack Property

The Page.IspostBack Boolean property indicates whether this page is loaded as a response to a round trip to the server, or it is being loaded for the first time. This property helps you to write the code needed for the first time the page is loaded, and avoiding running this same code each time the page is posted back. You can use this property efficiently in the page_load event. This event is executed each time a page is loaded, so you can use this property conditionally to avoid unnecessary re-running of certain code.

Server Control's AutoPostBack Property

Always set this property to false except when you really need to turn it on. This property automatically post back to the server after some action takes place depending on the type of the control. For example, in the Text Control this property automatically post back to the server after the text is modified which is a great deal of processing cost and hence much slower performance and most importantly a poor user experience.

Leave Buffering on

It is important to leave page buffering in its on state to improve your page speed, unless you have a serious reason to turn it off.

Server Controls View State

Server control by default saves all the values of its properties between round trips, and this increases both page size and processing time which is of course an undesired behavior. Disable the server control view state whenever possible. For example, if you bind data to a server control each time the page is posted back, then it is useful to disable the control's view state property. This reduces page size and processing time.

Methods for redirection

There are many ways you can use to redirect a user from the current page to another one in the same application, however the most efficient methods to do this are: the Server.Transfer method or cross-page posting.

Web Applications

The following topics give you some tips about how to make an efficient web application:

Precompilation

When an already deployed ASP.NET web application page is requested for the first time, that page needs to be compiled (by the server) before the user gets a response. The compiled page or code is then cached so that we need not to compile it again for the coming requests. It is clear that the first user gets a slow response than the following users. This scenario is repeated for each web page and code file within your web site.

When using precompilation then the ASP.NET entire web application pages and code files will be compiled ahead. So, when a user requests a page from this web application he will get it in a reasonable response time whatever he is the first user or not.

Precompiling the entire web application before making it available to users provides faster response times. This is very useful on frequently updated large web applications.

Encoding

By default ASP.NET applications use UTF-8 encoding. If your application is using ASCII codes only, it is preferred to set your encoding to ASCII to improve your application performance.

Authentication

It is recommended to turn authentication off when you do not need it. The authentication mode for ASP.NET applications is windows mode. In many cases it is preferred to turn off the authentication in the 'machin.config' file located on your server and to enable it only for applications that really need it.

Debug Mode

Before deploying your web application you have to disable the debug mode. This makes your deployed application faster than before. You can disable or enable debug mode form within your application's 'web.config' file under the 'system.web' section as a property to the 'compilation' item. You can set it to 'true' or 'false'.

Coding Practices

The following topics give you guidelines to write efficient code:

Page Size

Web page with a large size consumes more bandwidth over the network during its transfer. Page size is affected by the numbers and types of controls it contains, and the number of images and data used to render the page. The larger the slower, this is the rule. Try to make your web pages small and as light as possible. This will improve response time.

Exception Handling

It is better for your application in terms of performance to detect in your code conditions that may cause exceptions instead of relying on catching exceptions and handling them. You should avoid common exceptions like null reference, dividing by zero , and so on by checking them manually in your code.

The following code gives you two examples: The first one uses exception handling and the second tests for a condition. Both examples produce the same result, but the performance of the first one suffers significantly.

    8         ' This is not recommended.
    9         Try
   10             Output = 100 / number
   11         Catch ex As Exception
   12             Output = 0
   13         End Try
   14 
   15         ' This is preferred.
   16         If Not (number = 0) Then
   17             Output = 100 / number
   18         Else
   19             Output = 0
   20         End If

Garbage Collector

ASP.NET provides automatic garbage collection and memory management. The garbage collector's main task is to allocate and release memory for your application. There are some tips you can take care of when you writing your application's code to make the garbage collector works for your benefit:

Avoid using objects with a Finalize sub as possible and avoid freeing resources in Finalize functions.
Avoid allocating too much memory per web page because the garbage collector will have to do more work for each request and this increases CPU utilization (not to mention you can go out of memories in larger web applications)
Avoid having unnecessary pointers to objects because this makes these objects alive until you free them yourself within your code not in an automatic way.

Use Try / Finally

If you are to use exceptions anyway, then always use a try / finally block to handle your exceptions. In the finally section you can close your resources if an exception occurred or not. If an exception occurs, then the finally section will clean up your resources and frees them up.

String Concatenation

Many string concatenations are time consuming operations. So, if you want to concatenate many strings such as to dynamically build some HTML or XML strings then use the System.Text.StringBuilder object instead of system.string data type. The append method of the StringBuilder class is more efficient than concatenation.

Threading

If your application contains some operation that consumes time and resources, then instead of blocking the application flow awaiting for this process or operation to be finished it is recommended to create a separate thread for this blocking operation. By threading you will save your application normal flow from delays. Examples of time consuming operations that can be moved to another thread other than the main program thread are: querying on a database and waiting for results, and extensive IO operations.

For further information

Refer to the online copy of Microsoft Developers Network at http://msdn.microsoft.com or use your own local copy of MSDN.

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