title: MSTest, Targeting multiple Framework version
body: <p>We use TFS (2010) for Continuous Integration. Solution Contains .NET 4 ,and Silverlight 4 projects. Everything was working fine, until one day MSTest.exe stopped running UnitTest dlls, with this message : 
  <strong><em>A test run can only be targeted to single .Net framework version. Targeting multiple Framework version in single run is unsupported.</em></strong></p>
  
  <p><em><strong>What I did:</em></strong>
  I have checked to see if there has been any config changes in the solution, but discovered none. files with .Testsettings and .vsdmi are intact.</p>
  
  <p>Also we have three branches on TFS, which use same controller and Agent. and all the builds have stopped working. 
  I tried running MSTest from command-line, and same problem. seems if there are SL and .NET test dlls, MSTest does not work.</p>
  
  <p><strong>The complete log for MSTest is here :</strong></p>
  
  <p>Run MSTest for TestAssemblies</p>
  
  <pre><code>C:\Program Files\Microsoft Visual Studio 10.0\Common7\IDE\MSTest.exe /nologo /usestderr /testSettings:"C:\Builds\1\Product\Sources\OM\build.testsettings" /searchpathroot:"C:\Builds\1\Product\Binaries" /resultsfileroot:"C:\Builds\1\Product\TestResults" /testcontainer:"C:\Builds\1\Product\Binaries\OM.Views.Tests.dll" /testcontainer:"C:\Builds\1\Product\Binaries\OM.ApplicationServices.UnitTests.dll" /publish:"http://tfsServer:8080/tfs/DefaultCollection" /publishbuild:"vstfs:///Build/Build/3750" /teamproject:"Products" /platform:"Any CPU" /flavor:"Release" 
  Loading C:\Builds\1\Product\Sources\OM\build.testsettings...
  Loading C:\Builds\1\Product\Binaries\OM.ApplicationServices.UnitTests.dll...
  Loading C:\Builds\1\Product\Binaries\OM.ViewModels.Tests.dll...
  Starting execution...
  A test run can only be targeted to single .Net framework version. Targeting multiple Framework version in single run is unsupported.
  There are no results to be published.
  </code></pre>