This article was previously published under Q307513
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If an ASP.NET application uses a custom configuration section handler, a first chance exception of type access violation may occur in the Aspnet_wp.exe process (or W3wp.exe process, foran application that runs on Microsoft Internet Information Services [IIS] 6.0) when the ASP.NET application is under stress.
This problem can occur when multiple threads are accessing the same configuration object simultaneously if your implementation of the IConfigurationSectionHandler interface is not thread-safe and stateless or if the object that the Create method returns is not thread-safe and immutable.
When you create a custom ASP.NET configuration section handler, use the following guidelines when you implement the IConfigurationSectionHandler interface:
Instances of your class that implement the IConfigurationSectionHandler interface must be thread-safe and stateless.
The object that the IConfigurationSectionHandler.Create method returns must be thread-safe and immutable.
Do not modify the parent argument to the IConfigurationSectionHandler.Create method.
This behavior is by design.
Instances of IConfigurationSectionHandler must be thread-safe and stateless. You must be able to call the IConfigurationSectionHandler.Create method from multiple threads simultaneously.
Furthermore, the configuration object that IConfigurationSectionHandler.Create generates must be thread-safe and immutable. Because the configuration system caches the configuration objects, it is important that you not modify the "parent" argument to IConfigurationSectionHandler.Create. For example, if the return value of IConfigurationSectionHandler.Create is only a small modification of the "parent," you must modify a clone of the "parent," not the original.
For more information about ASP.NET configuration, click the following article numbers to view the articles in the Microsoft Knowledge Base: