title: No executable found matching command "dotnet-ef" error in a project without project.json file
body: <p>I've a <a href="https://msdn.microsoft.com/en-us/library/jj620922.aspx" rel="nofollow noreferrer">VSTO - AddIn</a> project developed using <code>VS2015-Update3</code>. I'm trying to <a href="https://msdn.microsoft.com/en-us/library/ms404815.aspx" rel="nofollow noreferrer">implement a Database functionality</a> in the project and for that I'm implementing <strong>EF Core</strong>. I'm  using the following official <a href="https://docs.microsoft.com/en-us/ef/core/get-started/netcore/new-db-sqlite" rel="nofollow noreferrer">MSDN tutorial</a>. But I'm getting the above error when I run the command <code>dotnet ef migrations add MyFirstMigration</code>.</p>
  
  <p><strong>Please Note</strong>: </p>
  
  <ol>
  <li>VSTO-AddIn projects do not have a project.json file.</li>
  <li>VSTO projects use Full .NET framework (I'm using .NET 4.6.2). But, as explained <a href="https://stackoverflow.com/questions/40716588/entity-framework-core-in-full-net">here</a>, one can use EF Core in a Full .NET framework.</li>
  </ol>