title: Msbuild fails building website project with an indirect reference to System.Runtime
body: <p>I am running into a dependency issue with MSBuild. I added a NuGet package for Microsoft.Tpl.Dataflow to a project in my solution. This is causing a build failure for a website project in the solution which references the first project. There seems to be an issue with getting the correct runtime version.</p>
  
  <p>This is one of the many errors I get when building the solution with MSBuild.</p>
  
  <blockquote>
    <p>C:\src\MyWebsite.metaproj : warning MSB3268: The primary reference
    "C:\src\projects\ReferencedProject\bin\Debug\ReferencedProject.dll"
    could not be resolved because it has an indirect dependency on the
    framework assembly "System.Runtime, Version=4.0.0.0, Culture=neutral,
    PublicKeyToken=b03f5f7f11d50a3a" which could not be resolved in the
    currently targeted framework. ".NETFramework,Version=v4.5". To resolve
    this problem, either remove the reference
    "C:\src\projects\ReferencedProject\bin\Debug\ReferencedProject.dll"
    or retarget your application to a framework version which contains
    "System.Runtime, Version=4.0.0.0, Culture=neutral,
    PublicKeyToken=b03f5f7f11d50a3a".</p>
  </blockquote>
  
  <p>The confusing thing to be is that the solution builds fine in Visual Studio. Also, all the other projects in the solution build—it's only the website projects that are failing.</p>
  
  <p>I have tried</p>
  
  <ul>
  <li>Changing the target framework for the website to 4.0 (it's currently 4.5).</li>
  <li>Adding an assembly reference to System.Runtime.dll version 4.0.0.0</li>
  </ul>
  
  <p>I still can't get it to build. How can I fix this?</p>