.Net MVC 4 Project fails with Event Log Error "The Module DLL C:\WINDOWS\system32\inetsrv\aspnetcore.dll failed to load. The data is the error."

Question

This is not a DotNetCore project (it's an MVC 4 project) and the app pool is properly configured to use dotnet CLR v4, yet after updating to a new version of Windows 10 (be it an insider build, or the new Anniversary Update), starting the app fails and the event log shows the following error:

The Module DLL C:\WINDOWS\system32\inetsrv\aspnetcore.dll failed to load. The data is the error.

I don't have any need for aspnetcore.dll yet. And removing references to the DLL for the site in IIS doesn't solve the problem. Any Tips?

Answer 1

Here's the easiest solution:

1. Search Cortana for Programs and Features to open the legacy Control Panel's installed applications list.
2. Find and click the entry for Microsfot .NET Core 1.0.0 - VS 2015 Tooling ...
   • My version is "Preview 2"... though if they don't fix this, you may have a newer version
3. Click Change.
4. Click Repair.

The source of this problem seems to be the build upgrade process for Windows 10, where it re-installs IIS... while it copies over all the site settings to the new applicationHost.config, it seems to break any non-standard modules you previously had installed. For example, this same problem also affects the URL Rewrite 2 module (which is also fixed by running a repair).

Hopefully the team at Microsoft who works on maintaining the IIS config between build updates will get a chance to fix this (they're tracking this bug on github here). Until then, you have to do this repair after installing any new Windows builds.

UPDATE: This bug has been fixed in Windows 10 Insider Build 15002, and will be released as part of the Windows 10 Creators Update on April 11, 2017. So, once you've solved this by following the steps above, you shouldn't run into it again with the next major Windows 10 update.

Answer 2

Download the DotNetCore.1.0.0.RC2-SDK.Preview1-x64.exe, execute and uninstall. After, go to Programs and Features e Repair the Microsoft.NET Core 1.0.0 RC2 - VS 2015 Tooling Preview 1. Work for me.