title: ASP.NET Core 3: How to reference 3.0.0 assemblies in custom libraries?
body: <p>I see that applications that reference the <code>Microsoft.AspNetCore.App</code> framework (AKA ASP.NET Core 3.0) uses types from the assembly <code>Microsoft.AspNetCore.Mvc.Abstractions, Version=3.0.0.0,</code></p>
  <p><a href="https://i.stack.imgur.com/RlJYr.png" rel="noreferrer"><img src="https://i.stack.imgur.com/RlJYr.png" alt="enter image description here" /></a></p>
  <p>But I can't find a NuGet package with same version <code>3.0.0</code>. How should I reference packages now? E.g. if I want to override <code>ControlBase</code>, how should I reference the <code>Microsoft.AspNetCore.Mvc.Core, Version=3.0.0.0</code> assembly if there are <a href="https://www.nuget.org/packages/Microsoft.AspNetCore.Mvc.Core/" rel="noreferrer">no such package versions on NuGet</a>?</p>
  <p>After adding the following:</p>
  <pre><code>  &lt;ItemGroup&gt;
      &lt;FrameworkReference Include=&quot;Microsoft.AspNetCore.App&quot; /&gt;
    &lt;/ItemGroup&gt;
  </code></pre>
  <p>I have another kind of waning:</p>
  <p><a href="https://i.stack.imgur.com/FwvJ2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/FwvJ2.png" alt="enter image description here" /></a></p>
  <p>Which gives the error:</p>
  <blockquote>
  <p><code>NETSDK1073</code>: The FrameworkReference 'Microsoft.AspNetCore.App' was not recognized    Routines.AspNetCore C:\Program Files\dotnet\sdk\3.0.100\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.FrameworkReferenceResolution.targets   263</p>
  </blockquote>
  <p>Unloading and reloading the application doesn't help.</p>
  <p>The same problem occurs in an empty new project:</p>
  <pre><code>&lt;Project Sdk=&quot;Microsoft.NET.Sdk&quot;&gt;
  
    &lt;PropertyGroup&gt;
      &lt;TargetFramework&gt;netstandard2.1&lt;/TargetFramework&gt;
    &lt;/PropertyGroup&gt;
  
    &lt;ItemGroup&gt;
      &lt;FrameworkReference Include=&quot;Microsoft.AspNetCore.App&quot; /&gt;
    &lt;/ItemGroup&gt;
  &lt;/Project&gt;
  </code></pre>
  <p>Compilation</p>
  <blockquote>
  <p>1&gt;------ Rebuild All started: Project: ClassLibrary1, Configuration: Debug Any CPU ------</p>
  <p>1&gt;C:\Program
  Files\dotnet\sdk\3.0.100\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.FrameworkReferenceResolution.targets(263,5):
  error NETSDK1073: The FrameworkReference 'Microsoft.AspNetCore.App'
  was not recognized 1&gt;Done building project &quot;ClassLibrary1.csproj&quot; --
  FAILED.
  ========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========</p>
  </blockquote>