title: Reusable PropertyGroup elements in a csproj file
body: <p>I have a series of properties I need to set in ~15 projects. Is there a way to put these properties in a single file and have all the project files reference the one file using some sort of import directive rather than duplicating the properties in each project file?</p>
  
  <p><strong>EDIT:</strong> To clarify, I'm talking about <code>&lt;PropertyGroup&gt;</code> elements within the csproj file. All the projects need the same series of <code>&lt;PropertyGroup&gt;</code> settings. These elements set properties like <code>DebugSymbols</code> or <code>DefineDebug</code>, and are not used for referencing source files.</p>