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Note   If you host an ASP.NET Web application built using the .NET Framework version 1.0, the process account needs appropriate permissions to the root of the current file system drive. For more information, see Microsoft Knowledge Base article 317955, "FIX: 'Failed to Start Monitoring Directory Changes' Error Message When You Browse to an ASP.NET Page."

• InProc - Fastest, but the more session data, the more memory is consumed on the web server, and that can affect performance.
• StateServer - When storing data of basic types (e.g. string, integer, etc), in one test environment it's 15% slower than InProc. However, the cost of serialization/deserialization can affect performance if you're storing lots
  of objects. You have to do performance testing for your own scenario.
• SQLServer - When storing data of basic types (e.g. string, integer, etc), in one test environment it's 25% slower than InProc. Same warning about serialization as in StateServer.

StateServer
• - In a web farm, make sure you have the same in all your web servers. See KB 313091 on how to do it.
• - Also, make sure your objects are serializable. See KB 312112 for details.
• - For session state to be maintained across different web servers in the web farm, the Application Path of the website (For example \LM\W3SVC\2) in the IIS Metabase should be identical in all the web servers in the web farm. See KB 325056 for details

The DataSet object implements ISerializable meaning that it provides for its own serialization format and data layout. And it does that using plain XML. (Not even blanks and tabs are removed.) As a result, when you remote a DataSet you are actually passing data using a large chunk of data made after a verbose schema--the DiffGram. No matter you use a binary channel and formatter.

This point is well addressed in the following KB article. Which, in turn, references an MSDN Magazine article of mine for further details. Both articles illustrate some workaround, the best of which I believe is using a compact-formatter that just zips everything being transferred.

The good news is that this seems to be fixed in 2.0. A new property--RemotingFormat--on DataSet and DataTable objects makes possible for you to interact with the implementation of ISerializable and choose a binary format to optimize performance in .NET Remoting scenarios.

Out-of-process Mode

Included with the .NET SDK is a Windows® NT service: ASPState. This Windows service is what ASP.NET uses for out-of-process session state management. To use this state manager, you first need to start the service. To start the service, open a command prompt and type:

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net start aspstate

What you'll see is:

Figure 1. Starting the Windows NT service ASPState at the command prompt

At this point, the Windows NT Service ASPState has started and is available to ASP.NET. Next, we need to configure ASP.NET to take advantage of this service. To do this we need to configure config.web:

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We changed only from inproc mode to stateserver mode. This setting tells ASP.NET to look for the ASP state service on the server specified in the server and port settings—in this case, the local server.

We can now call SessionState.aspx, set a session state value, stop and start the IIS process (iisreset), and continue to have access to the values for our current state.

A surrogate selector object has to implement the ISurrogateSelector interface (table 12.8) to interact with the runtime serialization formatters of the .NET Framework. The interface defines the GetSurrogate() method to retrieve serialization surrogates by object type and serialization scenario.

To register one or more selectors, the formatter exposes a property named SurrogateSelector. With surrogate selectors registered, the formatter iterates over all selectors to find a surrogate for the object type it has to process in the given context. If it can locate an appropriate surrogate it delegates serialization to the surrogate. Figure 12.1 illustrates this interaction between the formatter, the surrogate selector and the serialization surrogate.

Application objects can be integrated with the framework in two ways. By writing a surrogate for the object type and registering the surrogate with the framework, or by implementing INxSerializable. The framework provides a built-in surrogate for types that implement INxSerializable. For unknown types, native .NET serialization is used.

   ss.AddSurrogate(typeof(Car),       new StreamingContext(StreamingContextStates.All),       new CarSerializationSurrogate());   // NOTE: AddSurrogate can be called multiple times to register   // more types with their associated surrogate types   // 5. Have the formatter use our surrogate selector   formatter.SurrogateSelector = ss;

It is possible, however, to persist view state to an alternate medium. Such customizations were possible in ASP.NET version 1.x by overriding a couple of methods in the Page class. ASP.NET 2.0 makes customizing page state persistence easier as this logic is handled through a separate class. In this article we'll explore the built-in page state persistence options in ASP.NET 2.0, which includes the ability to persist page state to session state rather than through a hidden form field. We'll also look at how to extend the functionality to provide a custom persistence scheme. Read on to learn more!