title: Mixed mode assembly is built against 'v2.0.50727' error
body: <p>First of all, I've found the other posts on StackOverflow <a href="https://stackoverflow.com/questions/1604663/what-does-uselegacyv2runtimeactivationpolicy-do-in-the-net-4-config/2467255#2467255">here</a>, but it did not resolve my error.</p>
  
  <p>I have 3 different environments/domains with a build server in each location. My Dev and UAT environments build just fine, but the production version does not work.</p>
  
  <p>I'm getting the error</p>
  
  <blockquote>
    <p>Mixed mode assembly is built against version 'v2.0.50727' of the
    runtime and cannot be loaded in the 4.0 runtime without additional
    configuration information</p>
  </blockquote>
  
  <p>I've added this tag to my app.config file (which was the suggested fix in the link I have above)</p>
  
  <pre><code>  &lt;startup useLegacyV2RuntimeActivationPolicy="true"&gt;
      &lt;supportedRuntime version="v4.0"/&gt;
    &lt;/startup&gt;
  </code></pre>
  
  <p>What else could be different between my build servers/environments/domains that would be causing this issue?</p>
  
  <p>In response to Allen's question, I believe this is what you're asking:</p>
  
  <pre><code>&lt;Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"&gt;
    &lt;PropertyGroup&gt;
      &lt;Configuration Condition=" '$(Configuration)' == '' "&gt;Debug&lt;/Configuration&gt;
      &lt;Platform Condition=" '$(Platform)' == '' "&gt;x86&lt;/Platform&gt;
      &lt;ProductVersion&gt;8.0.30703&lt;/ProductVersion&gt;
      &lt;SchemaVersion&gt;2.0&lt;/SchemaVersion&gt;
      &lt;ProjectGuid&gt;{D3D87C05-2811-489B-9F0D-7676B6485AA0}&lt;/ProjectGuid&gt;
      &lt;OutputType&gt;Exe&lt;/OutputType&gt;
      &lt;AppDesignerFolder&gt;Properties&lt;/AppDesignerFolder&gt;
      &lt;RootNamespace&gt;MVST.Batch.CorrespondenceConversion&lt;/RootNamespace&gt;
      &lt;AssemblyName&gt;MVST.Batch.CorrespondenceConversion&lt;/AssemblyName&gt;
      &lt;TargetFrameworkVersion&gt;v3.5&lt;/TargetFrameworkVersion&gt;
      &lt;FileAlignment&gt;512&lt;/FileAlignment&gt;
    &lt;/PropertyGroup&gt;
  </code></pre>
  
  <p>I have over 100 other projects that are setup the exact same way and those build ok.</p>