PM> Add-Migration InitialDatabase dotnet exec needs a managed .dll or .exe extension. The application specified was 'C:\Users\xxxxxx\documents\visual studio 2017\Projects\TheWorld\src\TheWorld\bin\Debug\netcoreapp1.0\TheWorld.runtimeconfig.json' Process finished with non-zero exit code PM>
Visual Studio Version: 2017 RC
Project Dependencies :
I had the same problem. The only thing I had to do is changing the Target Framework in the Project properties.
I hope this helps.
In VS2017RC - All I had to do was install .NetCore again using Package Manager Console:
Later migration script worked and "dotnet exec needs a managed .dll or .exe extension." error went away.