title: Missing "Add as Link" in "Add Existing Item" for Visual Studio 2015 Shared projects
body: <p><strong>Context:</strong></p>
  
  <p>Classic project types have an "Add as Link" option in the "Add Existing Item" dialog. This allows one file to be shared across multiple projects, by adding the file to the project without physically copying the file to the project directory. This button is missing from the Add Existing Item dialog for Shared projects. See exhibit below.</p>
  
  <p><strong><em>Note</em></strong>: <em>This is not such new ASP 5 project with "project.json". There is no "project.json", Project files are XML though named</em> *.projitems, <em>their XML schema is very similar to</em> <em>.csproj</em> </p>
  
  <p><strong>Question:</strong></p>
  
  <p>In my solution there are multiple shared projects. I would like to have a single common solution level file (such as SolutionAssemblyInfo.cs) linked into each one. How can I accomplish this task?</p>
  
  <p><strong>Exhibit:</strong></p>
  
  <p><a href="https://i.stack.imgur.com/jyMdp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jyMdp.png" alt="enter image description here"></a></p>