title: Add existing project from GitHub to my local Visual Studio Solution
body: <p>I have a local Solution developed in Visual Studio. It is also published in GitHub (<a href="https://github.com/symasdesign/DiagramTest" rel="nofollow noreferrer">https://github.com/symasdesign/DiagramTest</a>). Now I want to add another project from GitHub (<a href="https://github.com/symasdesign/stateless" rel="nofollow noreferrer">https://github.com/symasdesign/stateless</a>).</p>
  
  <p>For this, I have added the project stateless as a submodule to DiagramTest with </p>
  
  <pre><code>...\DiagramTest&gt;git submodule add https://github.com/symasdesign/stateless.git
  </code></pre>
  
  <p>The Solution <code>stateless.sln</code> is now added in a subdirectory to <code>...\DiagramTest</code>:</p>
  
  <pre><code>...\DiagramTest\stateless\Stateless.sln
  </code></pre>
  
  <p>It contains the project <code>Stateless.csproj</code> at </p>
  
  <pre><code>...\DiagramTest\stateless\src\Stateless\Stateless.csproj
  </code></pre>
  
  <p>When I add this project to my Solution <code>DiagramTest</code>, I get the following error in Visual Studio:</p>
  
  <pre><code>Assets file '...\DiagramTest\stateless\src\Stateless\obj\project.assets.json' not found. Run a NuGet package restore to generate this file.
  </code></pre>
  
  <p>When I run "Restore NuGet Packages" I get the error</p>
  
  <pre><code>Error occurred while restoring NuGet packages: The operation failed as details for project Stateless could not be loaded.               
  </code></pre>
  
  <p>What do I wrong for adding the foreign project to my solution and get it working?</p>