How to fix "HTTP Error 500.0 - ANCM In-Process Handler Load Failure"

"HTTP Error 500.0 - ANCM In-Process Handler Load Failure" typically occurs in ASP.NET Core applications when the ASP.NET Core Module (ANCM) fails to load the in-process hosting handler.

HTTP Error 500.0 - ANCM In-Process Handler Load Failure

Troubleshooting steps:

Check the system event log for error messages

Enable logging the application process' stdout messages

Attach a debugger to the application process and inspect

Here are some steps you can take to troubleshoot and fix this issue:

Ensure that the ASP.NET Core Hosting Bundle is installed on the server. You can download it from the Microsoft website.

Make sure that the application pool hosting your ASP.NET Core application is configured to use the correct .NET CLR version (typically .NET CLR v4.0.xxxx). Verify that the application pool identity has appropriate permissions to access the application's files and resources.

Ensure that the correct version of the .NET Core runtime is installed on the server. If your application targets a specific version of the .NET Core runtime, make sure it is installed and correctly configured.

Ensure that your application's configuration files (such as Web.config for ASP.NET Core MVC applications or appsettings.json for ASP.NET Core Web API applications) are correctly configured.

Open you Web.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <location path="." inheritInChildApplications="false">
    <system.webServer>
      <handlers>
        <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModuleV2" resourceType="Unspecified" />
      </handlers>
      <aspNetCore processPath=".\ERegist.exe" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" hostingModel="InProcess" />
    </system.webServer>
  </location>
</configuration>

Next, change AspNetCoreModuleV2 to AspNetCoreModule

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <location path="." inheritInChildApplications="false">
    <system.webServer>
      <handlers>
        <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />
      </handlers>
      <aspNetCore processPath=".\ERegist.exe" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" hostingModel="InProcess" />
    </system.webServer>
  </location>
</configuration>

If your application uses any third-party dependencies or libraries, make sure they are correctly referenced and compatible with the version of ASP.NET Core you are using.

Sometimes, simply restarting the IIS server can resolve the issue.

If none of the above steps resolve the issue, try updating or reinstalling the ASP.NET Core runtime on the server. Sometimes, a corrupted installation can cause such errors.

By following these steps, you should be able to diagnose and fix the "HTTP Error 500.0 - ANCM In-Process Handler Load Failure" in your ASP.NET Core application.