Session data is lost when you use ASP.NET InProc session state mode

This article helps you resolve the problem that session data is lost when you use ASP.NET InProc session state mode.

Original product version:   ASP.NET
Original KB number:   324772

Symptoms

Session data for ASP.NET Web applications appears to be lost at random intervals for the InProc session state mode.

Cause

Session state data is lost if the AppDomain class or the Aspnet_wp.exe process (or the W3wp.exe process, for applications that run on IIS 7.0 or a later version) is recycled. Generally, the AppDomain is restarted based on several factors:

• Various attributes (for example, the memoryLimit attribute) have particular settings in the <processModel> section of the configuration file.
• The Global.asax or the Web.config file was modified.
• The Bin directory of the Web application was modified.
• Virus scanning software touched some .config files.

InProc session mode indicates that session state is stored locally. This means that with InProc session state mode is stored as life objects in the AppDomain of the Web application. This is why the session state is lost when Aspnet_wp.exe (or W3wp.exe, for applications that run on IIS) or the AppDomain restarts.

Resolution

To work around this problem, you can use StateServer or SqlServer session state mode. ASP.NET provides these other approaches for storing session state data. In the StateServer and SqlServer modes, your session state is not stored in the AppDomain of the Web application.

Status

This behavior is by design.

References

For more information about ASP.NET session state management and other related information, see Session State.