title: Use a single Visual Studio solution to build both x86 and x64 at the same time for C++/CLI project
body: <p>As a follow-up to this question:
  <a href="https://stackoverflow.com/questions/1574075/use-a-single-visual-studio-solution-to-build-both-x86-and-x64-at-the-same-time">Use a single Visual Studio solution to build both x86 and x64 at the same time?</a></p>
  
  <p>I'm using the technique in the accepted answer for C# projects and it works great.  <strong>Is there a way to do the same thing for C++/CLI project (.vcxproj)?</strong>  Using that technique doesn't seem to work (the "BeforeBuild" and "AfterBuild" targets seem to be ignored).</p>
  
  <p>I'd even be okay with having the task be executed from the Before/AfterBuild Target of another C# project in the solution:</p>
  
  <pre><code>&lt;Target Name="BeforeBuild"&gt;
    &lt;MSBuild Condition=" '$(Platform)' == 'x64' " Projects="MyCPPCLIProject.vcxproj" Properties="Platform=x86;" /&gt;
  &lt;/Target&gt;
  </code></pre>
  
  <p>When I do this, I get the following error (even though the project is in the solution):</p>
  
  <pre><code>C:\VS\MyCSProj.csproj(1773,5): error MSB3202: The project file "MyCPPCLIProject.vcxproj" was not found.
  </code></pre>