title: Web Site: MSB3270: There was a mismatch between the processor architecture
body: <p>I have a Web Forms Web Site project. This web site references 4 class library projects. 3 of these class libraries reference a third-party assembly. I am getting the following compiler error for each of the 3 class library projects.</p>
  
  <blockquote>
    <p>ASPNETCOMPILER : error ASPCONFIG: Could not load file or assembly
    'myAssembly' or one of its dependencies. An attempt was made to load a
    program with an incorrect format. [Project.
        metaproj]</p>
  </blockquote>
  
  <p>I have tried all possible combinations of AnyCPU/x86/x64 on the class library projects. I cannot change this on the Web Site project. I have both a x86 and x64 version of the third-party dll. Tried both.</p>
  
  <blockquote>
    <p>"ClassLibrary.csproj" (default target) (4) ->
        (ResolveAssemblyReferences target) ->
          C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1561,5
        ): warning MSB3270: There was a mismatch between the processor architecture of
        the project being built "MSIL" and the processor architecture of the reference
        "ThirdPartyDll, Version=xxx, Culture=neutral, processorArchitectu
        re=x86", "x86". This mismatch may cause runtime failures. Please consider chang
        ing the targeted processor architecture of your project through the Configurati
        on Manager so as to align the processor architectures between your project and
        references, or take a dependency on references with a processor architecture th
        at matches the targeted processor architecture of your project. [ClassLibrary.cspro
        j]</p>
  </blockquote>
  
  <p>The bellow illustrates the solution configuration. Note I cannot change from "AnyCPU" here, only from within each individual class library project.</p>
  
  <p><img src="https://i.stack.imgur.com/pyS8E.png" alt="Solution configuration"></p>
  
  <p>All .NET 4</p>
  
  <p>Converting the Web Site to a Web Application is not an option.</p>
  
  <p>Thanks,</p>