[asp.net] IIS 7, HttpHandler and HTTP Error 500.21

On IIS 7, I'm trying to use custom HttpHandler for my ASP.NET web application. I use pipeline mode "classic", .NET version is 4.0.30319, my web.config configuration for the handler is:

<system.webServer>
<handlers>
    <add name="MyHandler" path="*.myExtension" verb="*" type="Company.App.UI.Controls.MyHandler, Company.App.UI" resourceType="Unspecified" />
</handlers>
</system.webServer> 

When I invoke this handler, I get this error:

HTTP Error 500.21 - Internal Server Error
Handler "MyHandler" has a bad module "ManagedPipelineHandler" in its module list

I did a google search, the most of people fix this issue by re-registering ASP.NET by aspnet_regiis.exe /i command, but this is not working for me (the command finishes, I restart the IIS, but same error). I tried it on two different servers, but got the same result.

What else should I try? Thank you

On windows server 2016 i have used:

dism /online /enable-feature /featurename:IIS-ASPNET45 /all

Also can be done via Powershell:

Install-WindowsFeature .NET-Framework-45-Features

One solution that I've found is that you should have to change the .Net Framework back to v2.0 by Right Clicking on the site that you have manager under the Application Pools from the Advance Settings.

This situation happens because you haven't installed/start service of ASP.net.

Use below command in windows 7,8,10.

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

Luckily, it’s very easy to resolve. Run the follow command from an elevated command prompt:

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

If you’re on a 32-bit machine, you may have to use the following:

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

I had the same problem and just solved it. I had posted my own question on stackoverflow:

Can't PUT to my IHttpHandler, GET works fine

The solution was to set runManagedModulesForWebDavRequests to true in the modules element. My guess is that once you install WebDAV then all PUT requests are associated with it. If you need the PUT to go to your handler, you need to remove the WebDAV module and set this attribute to true.

<modules runManagedModulesForWebDavRequests="true">
...
</modules>

So if you're running into the problem when you use the PUT verb and you have installed WebDAV then hopefully this solution will fix your problem.

I had the same problem and was solved by running the following in run

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