A reference to could not be added ´. An assembly must have a dll or exe extension in order to be referenced

Question

I have plain c# console application (.NET 4.6) where I want to reference a .NET Core Class Library:

{
  "version": "1.0.0-*",

  "dependencies": {
    "NETStandard.Library": "1.6.0",
    "Newtonsoft.Json": "9.0.1"
  },

  "frameworks": {
    "netstandard1.4": {
      "imports": "dnxcore50"
    }
  }
}

And I get the following exception:

Answer 1

Simple solution:

My .NET console application uses .NET 4.6 and should reference a Core Class Library using .NET Platform Standard 1.4.

Mapping the .NET Platform Standard to platforms says that .NET 4.6 is compatible with .NET Platform Standard 1.3.

Changing the project.json of the Core Class Library to (excerpt)

"frameworks": {
    "netstandard1.3": {
      "imports": "dnxcore50"
    }
  }

solved the problem.

Here is a compatibility table demonstrating the problem (.NET 4.6 is compatible with .NET Platform Standard <= 1.3):