Using PrecompiledMvcEngine FindView throws Invalid

问题:

I got an InvalidOperationException when the MVC controller tried to FindView while using the PrecompiledMvcEngine.

Using on a machine that has VS2012, MVC4 and deployed to IIS

回答1:

After looking at the source code of ControllerBase.FindView to ViewEngineCollection.FindView to VirtualPathProviderViewEngine to PrecompiledMvcEngine, found that _mappings in PrecompiledMvcEngine had a count of 0. (Tx to Reflection and Open source.)

The reason is that there was not Type assignable to WebPageRenderingBase in my project's DLL. On decompiling my dll, it actually had the compiled views, and the views extended from WebPageRenderingBase.

After writing a unit test to do the same thing that PrecompiledMvcEngine does to load views, found that they are using different versions of the WebPageRenderingBase class. RazorGenerator.Mvc uses System.Web.WebPages v1.0.0.0 to precompile at build time. The PrecompiledMvcEngine uses System.Web.WebPages v2.0.0.0 when loading types from the compiled assembly. Fixed this by changing my MVC csproject to also load v1.0.0.0 at runtime.

Changed

 <Reference Include="System.Web.WebPages" />

which picked up 2.0.0.0 to

 <Reference Include="System.Web.WebPages, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL" />

forcing it to always pick up 1.0.0.0. This problem will often be faced if you are deploying precompiled views to a machine with VS2012 and MVC4 installed, without specifying the correct version in the csproj file