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Debugging bad assemblies in IIS

Nick Gully

If you ever playing in IIS and encounter an intractible assembly error from components that look and seem just fine when you inspect their versions, signatures, and work when running inside Visual Studio:

Failed to complete setup of assembly (hr = 0x80070057). Probing terminated.

It might be that IIS's cached copy of the DLL is corrupted. Navigate into

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files

With IIS stopped, and blow away the root folder here. This will force IIS when it starts back up to rebuild it's own cache and take the good files from your project.