Use Session State Only If You Need To

One extremely powerful feature of ASP.NET is its ability to store session state for users, such as a shopping cart on an e-commerce site or a browser history. Since this is on by default, you pay the cost in memory even if you don't use it. If you're not using Session State, turn it off and save yourself the overhead by adding <@% EnabledSessionState = false %> to your ASP. This comes with several other options, which are explained at the ASP. NET Web site.

For pages that only read session state, you can choose EnabledSessionState=readonly. This carries less overhead than full read/write session state, and is useful when you need only part of the functionality and don't want to pay for the write capabilities.Use View State Only If You Need To

An example of View State might be a long form that users must fill out: if they click Back in their browser and then return, the form will remain filled. When this functionality isn't used, this state eats up memory and performance. Perhaps the largest performance drain here is that a round-trip signal must be sent across the network each time the page is loaded to update and verify the cache. Since it is on by default, you will need to specify that you do not want to use View State with <@% EnabledViewState = false %>. You should read more about View State on the the ASP. NET Web site to learn about some of the other options and settings to which you have access.Avoid STA COM

Apartment COM is designed to deal with threading in unmanaged environments. There are two kinds of Apartment COM: single-threaded and multithreaded. MTA COM is designed to handle multithreading, whereas STA COM relies on the messaging system to serialize thread requests. The managed world is free-threaded, and using Single Threaded Apartment COM requires that all unmanaged threads essentially share a single thread for interop. This results in a massive performance hit, and should be avoided whenever possible. If you can't port the Apartment COM object to the managed world, use <@%ASPCompat = "true" %> for pages that use them. For a more detailed explanation of STA COM, see the MSDN Library.Batch Compile

Always batch compile before deploying a large page into the Web. This can be initiated by doing one request to a page per directory and waiting until the CPU idles again. This prevents the Web server from being bogged down with compilations while also trying to serve out pages. Remove Unnecessary Http Modules

Depending on the features used, remove unused or unnecessary http modules from the pipeline. Reclaiming the added memory and wasted cycles can provide you with a small speed boost.Avoid the Autoeventwireup Feature

Instead of relying on autoeventwireup, override the events from Page. For example, instead of writing a Page_Load() method, try overloading the public void OnLoad() method. This allows the run time from having to do a CreateDelegate() for every page.Encode Using ASCII When You Don't Need UTF

By default, ASP.NET comes configured to encode requests and responses as UTF-8. If ASCII is all your application needs, eliminated the UTF overhead can give you back a few cycles. Note that this can only be done on a per-application basis.Use the Optimal Authentication Procedure

There are several different ways to authenticate a user and some of more expensive than others (in order of increasing cost: None, Windows, Forms, Passport). Make sure you use the cheapest one that best fits your needs.Tips for Porting and Developing in Visual Basic

A lot has changed under the hood from Microsoft® Visual Basic® 6 to Microsoft® Visual Basic® 7, and the performance map has changed with it. Due to the added functionality and security restrictions of the CLR, some functions are simply unable to run as quickly as they did in Visual Basic 6. In fact, there are several areas where Visual Basic 7 gets trounced by its predecessor. Fortunately, there are two pieces of good news: Most of the worst slowdowns occur during one-time functions, such as loading a control for the first time. The cost is there, but you only pay it once. There are a lot of areas where Visual Basic 7 is faster, and these areas tend to lie in functions that are repeated during run time. This means that the benefit grows over time, and in several cases will outweigh the one-time costs.

The majority of the performance issues come from areas where the run time does not support a feature of Visual Basic 6, and it has to be added to preserve the feature in Visual Basic 7. Working outside of the run time is slower, making some features far more expensive to use. The bright side is that you can avoid these problems with a little effort. There are two main areas that require work to optimize for performance, and few simple tweaks you can do here and there. Taken together, these can help you step around performance drains, and take advantage of the functions that are much faster in Visual Basic 7.Error Handling

The first concern is error handling. This has changed a lot in Visual Basic 7, and there are performance issues related to the change. Essentially, the logic required to implement OnErrorGoto and Resume is extremely expensive. I suggest taking a quick look at your code, and highlighting all the areas where you use the Err object, or any error-handling mechanism. Now look at each of these instances, and see if you can rewrite them to use try/catch. A lot of developers will find that they can convert to try/catch easily for most of these cases, and they should see a good performance improvement in their program. The rule of thumb is "if you can easily see the translation, do it."

Here's an example of a simple Visual Basic program that uses On Error Goto compared with the try/catch version.

Sub SubWithError()

On Error Goto SWETrap Dim x As Integer Dim y As Integer x = x / ySWETrap: Exit Sub End Sub Sub SubWithErrorResumeLabel() On Error Goto SWERLTrap Dim x As Integer Dim y As Integer x = x / y SWERLTrap: Resume SWERLExit End SubSWERLExit: Exit Sub

Sub SubWithError()

Dim x As Integer Dim y As Integer Try x = x / y Catch Return End Try End Sub Sub SubWithErrorResumeLabel() Dim x As Integer Dim y As Integer Try x = x / y Catch Goto SWERLExit End Try SWERLExit: Return End Sub

The speed increase is noticeable. SubWithError() takes 244 milliseconds using OnErrorGoto, and only 169 milliseconds using try/catch. The second function takes 179 milliseconds compared to 164 milliseconds for the optimized version.Use Early Binding

The second concern deals with objects and typecasting. Visual Basic 6 does a lot of work under the hood to support casting of objects, and many programmers aren't even aware of it. In Visual Basic 7, this is an area that out of which you can squeeze a lot of performance. When you compile, use early binding. This tells the compiler to insert a Type Coercion is only done when explicitly mentioned. This has two major effects: Strange errors become easier to track down. Unneeded coercions are eliminated, leading to substantial performance improvements.

When you use an object as if it were of a different type, Visual Basic will coerce the object for you if you don't specify. This is handy, since the programmer has to worry about less code. The downside is that these coercions can do unexpected things, and the programmer has no control over them.

There are instances when you have to use late binding, but most of the time if you're not sure then you can get away with early binding. For Visual Basic 6 programmers, this can be a bit awkward at first, since you have to worry about types more than in the past. This should be easy for new programmers, and people familiar with Visual Basic 6 will pick it up in no time.Turn On Option Strict and Explicit

With Option Strict on, you protect yourself from inadvertent late binding and enforce a higher level of coding discipline. For a list of the restrictions present with Option Strict, see the MSDN Library. The caveat to this is that all narrowing type coercions must be explicitly specified. However, this in itself may uncover other sections of your code that are doing more work than you had previously thought, and it may help you stomp some bugs in the process.

Option Explicit is less restrictive than Option Strict, but it still forces programmers to provide more information in their code. Specifically, you must declare a variable before using it. This moves the type-inference from the run time into compile time. This eliminated check translates into added performance for you.

I recommend that you start with Option Explicit, and then turn on Option Strict. This will protect you from a deluge of compiler errors, and allow you to gradually start working in the stricter environment. When both of these options are used, you ensure maximum performance for your application.