ASP.NET initialization by non-HTTP protocols causes HTTP 500.21 error in IIS

Consider the following scenario:

• An ASP.NET application is hosted under IIS7 or IIS7.5.
• The ASP.NET application makes both HTTP and non-HTTP WCF calls (such as netNamedPipeBinding or netTcpBinding).
• The first request to the ASP.NET application is a non-HTTP WCF call.

 

In this scenario, IIS will respond with an HTTP 500.21 status for all HTTP requests subsequent to the first non-HTTP WCF call.

 

When ASP.NET is hosted under IIS7 or IIS7.5, the runtime initialization can be either in Integrated or Classic mode, but only if the initialization is activated by an HTTP request. When ASP.NET is initialized based on non-HTTP Windows Process Activation Service (WAS) methods, the runtime is not fully initialized in either Integrated or Classic mode for HTTP requests.

 

To work around this problem, isolate the HTTP and non-HTTP applications by hosting them in separate IIS application pools.

 

Microsoft has confirmed that this is a problem with the products listed in the Applies To section.

 

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