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Editorial Team
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Asked: 2026-05-22T16:46:49+00:00

I am currently developing an ASP.net application which was started in version .Net framework

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I am currently developing an ASP.net application which was started in version .Net framework version 3.5. This worked fine without problems. However, I have now realised I need to use .Net framework version 4. When I change the project to be a .net 4 application and I try to run the web app from visual studio 2010 it displays

Unable to start debugging on the web
server. See help for common
configuration errors. Running the web
page outside the debugger may provide
more information.

Make sure the server is operating
properly…

I have changed the application pool for the web app to be .Net version 4 with integrated code. Visual studio still displays the error and when I try to run the web app from outside visual studio, directly running it from the browser I get an IIS error message which says

HTTP Error 500.21 Internal Server Error
Handler “PageHandlerFactory-Integrated” has a bad module “ManagedPipelineHandler” in its module list

This is running IIS7 on Windows 7.

Does anyone have any solutions as to how I can fix this problem

Thanks for your help

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1 Answer

  1. Editorial Team

    I had this exact same issue 2 days ago. I’m willing to bet it’s because you installed IIS after installing .NET 4.0.

    You can fix this by re-installing .NET 

    %windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe –i

    Or for 32bit

    %windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe –i

    Edit: Here’s the link I found and used the other day.

    http://www.gotknowhow.com/articles/fix-bad-module-managedpipelinehandler-in-iis7

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