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MS-Windows Troubleshooting

Error: Sys. WebForms. PageRequestManagerServerErrorException


When trying to run a .NET web-application which uses Ajax either:

  • the following error is generated in the browser:

    Error: Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code returned from the server was: 500

  • Nothing appears to happen in response to some interaction on the page. (The above error is being generated if you hunt for it - either by enabling notification of script errors in IE or using the Error Console in FireFox.)


This error (or behaviour) is caused by the interaction between Ajax and the WebServer when the WebServer generates an error and thus the response from the server is not handled by the Ajax JavaScript. The problem is caused by an error in the underlying VB.NET or C#, but is being masked because of the use of Ajax.


Attempt to reproduce the problem while debugging in the Visual Studio environment. The underlying error will then become apparent, allowing you to address it.

These notes have been tested within Microsoft Visual Studio .NET 2008 running under Windows Vista, and may apply to other versions as well.

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