MVCBuildViews not working correctly

I had this problem a few days ago and I fixed it by deleting obj/Debug folder. Cleaning the project also works. I have no idea about the cause of the issue, though.

See Joe Cartano's answer for a more permanent solution.

This problem occurs when there is web project output (templated web.config or temporary publish files) in the obj folder. The ASP.NET compiler used isn't smart enough to ignore stuff in the obj folder, so it throws errors instead.

Another fix is to nuke the publish output right before calling <AspNetCompiler>. Open your .csproj and change this:

<Target Name="MvcBuildViews" AfterTargets="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
  <AspNetCompiler VirtualPath="temp" PhysicalPath="$(WebProjectOutputDir)" />
</Target>

to this:

<Target Name="MvcBuildViews" AfterTargets="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
  <ItemGroup>
    <ExtraWebConfigs Include="$(BaseIntermediateOutputPath)\**\web.config" />
    <ExtraPackageTmp Include="$([System.IO.Directory]::GetDirectories(&quot;$(BaseIntermediateOutputPath)&quot;, &quot;PackageTmp&quot;, System.IO.SearchOption.AllDirectories))" />
  </ItemGroup>
  <Delete Files="@(ExtraWebConfigs)" />
  <RemoveDir Directories="@(ExtraPackageTmp)" />
  <AspNetCompiler VirtualPath="temp" PhysicalPath="$(WebProjectOutputDir)" />
</Target>

That will delete all web.configs under \obj, as well as all PackageTmp folders under \obj.

UPDATE:

Even better, based off https://stackoverflow.com/a/48582282/8037 you can exclude the obj folder entirely. Apparently the <AspNetCompiler /> task doesn't have an exclude parameter, but if you switch to calling the aspnet_compiler .exe directly, you can exclude obj like this:

<Target Name="MvcBuildViews" AfterTargets="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
    <Exec Command="$(MSBuildFrameworkToolsPath)aspnet_compiler.exe -v temp -p $(WebProjectOutputDir) -x $(BaseIntermediateOutputPath)"/>
</Target>