title: Compile error on TFS - defined in an assembly is not referenced
body: <p>We have a c# solution (framework 4.5.2), developed on a desktop, compiled on TFS server 2015. We added a new DLL project to it (framework 4.6.1), which uses the Microsoft Code Analysis package. The solution is being compiled with no problem on the desktop (VS 2017). We committed the changes to TFS, where it drops several compiler errors, e.g.:</p>
  
  <blockquote>
    <p>The type 'ValueType' is defined in an assembly that is not referenced.
    You must add a reference to assembly 'netstandard, Version=2.0.0.0,
    Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.</p>
  </blockquote>
  
  <p>The project contains several references according to word "netstandard":</p>
  
  <pre><code>&lt;Reference Include="Microsoft.CodeAnalysis, Version=2.10.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL"&gt;
    &lt;HintPath&gt;..\packages\Microsoft.CodeAnalysis.Common.2.10.0\lib\netstandard1.3\Microsoft.CodeAnalysis.dll&lt;/HintPath&gt;
  &lt;/Reference&gt;
  
  
  &lt;Reference Include="System.Collections.Immutable, Version=1.2.3.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL"&gt;
    &lt;HintPath&gt;..\packages\System.Collections.Immutable.1.5.0\lib\netstandard2.0\System.Collections.Immutable.dll&lt;/HintPath&gt;
  &lt;/Reference&gt;
  </code></pre>
  
  <p>When I added the the reference:</p>
  
  <pre><code>&lt;Reference Include="netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51" /&gt;
  </code></pre>
  
  <p>the compile errors still reported. On the desktop the solution still compiles without warnings or errors. What to do next?</p>
  
  <p>PS: Unfortunately, the framework versions are mixed in the solution. The 4.5.2 is preferred, but there was no chance to add MS Code Analysis package to a dll project with this version. :( Is the multiple framework versions the root cause of the problem?</p>