title: Why is this NuGet dependency missing when compiling .NET Framework project depending on .NET Standard?
body: <p>I have a Visual Studio solution, with 3 projects. </p>
  
  <p>The top level is a .NET Framework 4.6.1 Console App (Project A).
  It depends on a .NET Framework 4.6.1 Class Library (Project B).
  Project B depends on a .NET Standard 2.0 Class Library (Project C).</p>
  
  <p>I have some code in Project C that uses System.Data.SqlClient (NuGet package version 4.6.1).</p>
  
  <p>Due to the following known issue <a href="https://github.com/dotnet/sdk/issues/901" rel="noreferrer">https://github.com/dotnet/sdk/issues/901</a> I have also added System.Data.SqlClient as a NuGet dependency to Project B (the .NET Framework Class Library).</p>
  
  <p>This is Scenario 1, and when the solution is built, System.Data.SqlClient is copied to the /bin/Debug folder of Project A and the the application runs successfully.</p>
  
  <p>The code for Scenario 1 is here <a href="https://github.com/JamesDunlop/TestDependencyFlowsNetStandard" rel="noreferrer">https://github.com/JamesDunlop/TestDependencyFlowsNetStandard</a></p>
  
  <p>However, for Scenario 2, I now ADD a project reference to Project A such that it now also directly references/depends-on Project C (i.e. the .NET Standard Class Library), as well as Project B. This mimics what I will need to do in a legacy application.</p>
  
  <p>Clean, and rebuild and run. System.Data.SqlClient is now missing from the /bin/Debug folder of Project A, and at run time there is an exception "System.IO.FileNotFoundException: 'Could not load file or assembly 'System.Data.SqlClient"</p>
  
  <p>Why does the System.Data.SqlClient not get copied to /bin/Debug ?</p>
  
  <p>Note that I have chosen NOT to migrate the .NET Framework projects to PackageReferences in order to resolve the issue <a href="https://github.com/dotnet/sdk/issues/901" rel="noreferrer">https://github.com/dotnet/sdk/issues/901</a>, since I need to implement this in a large legacy ASP.NET solution where it is not feasible.</p>
  
  <p>I would expect that adding a reference to Project C would have little effect, other than (as observed) it results in a lot more type-forwarding DLLs being copied to the /bin/Debug folder. But I would not expect System.Data.SqlClient to now be missing.</p>