title: The type [Type] exists in both [Assembly1] and [netstandard 2.0 assembly]
body: <p>I cannot get Microsoft.EntityFrameworkCore 2.0 to work with NETStandard.Library 2.0</p>
  
  <blockquote>
    <p>Error CS0433  The type 'AttributeUsageAttribute' exists in both 'System.Runtime, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' and 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'  Contrived.Model.Schema  D:\Contrived\Contrived\Framework\Contrived.Model.Schema\Attributes\EntityColumnAttribute.cs</p>
  </blockquote>
  
  <p>My .csproj:</p>
  
  <pre><code>&lt;Project Sdk="Microsoft.NET.Sdk"&gt;
  
    &lt;PropertyGroup Label="Globals"&gt;
      &lt;SccProjectName&gt;SAK&lt;/SccProjectName&gt;
      &lt;SccProvider&gt;SAK&lt;/SccProvider&gt;
      &lt;SccAuxPath&gt;SAK&lt;/SccAuxPath&gt;
      &lt;SccLocalPath&gt;SAK&lt;/SccLocalPath&gt;
    &lt;/PropertyGroup&gt;
  
    &lt;PropertyGroup&gt;
      &lt;TargetFramework&gt;netstandard2.0&lt;/TargetFramework&gt;
    &lt;/PropertyGroup&gt;
  
    &lt;ItemGroup&gt;
      &lt;PackageReference Include="Microsoft.EntityFrameworkCore.Relational" Version="2.0.0" /&gt;
    &lt;/ItemGroup&gt;
  
    &lt;ItemGroup&gt;
      &lt;PackageReference Update="NETStandard.Library" Version="2.0.0" /&gt;
    &lt;/ItemGroup&gt;
  
  &lt;/Project&gt;
  </code></pre>
  
  <p>This also happens if i create a new solution and a netstandard 2.0 library then add entityframeworkcore 2.0</p>
  
  <blockquote>
    <p>Error CS1703  Multiple assemblies with equivalent identity have been imported: 'D:\Users\maksymiuk_a.nuget\packages\netstandard.library\2.0.0\build\netstandard2.0\ref\System.Threading.Tasks.dll' and 'D:\Users\maksymiuk_a.nuget\packages\system.threading.tasks\4.3.0\ref\netstandard1.3\System.Threading.Tasks.dll'. Remove one of the duplicate references.    ClassLibrary1   D:\Contrived\Contrived\ClassLibrary1\ClassLibrary1\CSC</p>
  </blockquote>