title: What is NuGetPackageImportStamp for?
body: <p>When adding certain NuGet packges to a project, sometimes a strange item appears in the first property group of the .csproj file.</p>
  
  <pre><code>&lt;PropertyGroup&gt;
    ...
    &lt;NuGetPackageImportStamp&gt;3d051ef3&lt;/NuGetPackageImportStamp&gt;
  &lt;/PropertyGroup&gt;
  </code></pre>
  
  <p>The stamp is different every time, and doesn't appear to be sequential.</p>
  
  <p>I can't find any reference to <code>&lt;NuGetPackageImportStamp&gt;</code> in the NuGet documentation.  What is it for and how does it work?  Is it necessary?</p>
  
  <p>One package that appears to add this every time is <a href="https://www.nuget.org/packages/StyleCop.MSBuild/">StyleCop.MSBuild</a>, at least with the current 4.7.49 version.  Simply add that package to a new project and you'll see this mystery item appear in your project file.</p>