dotnet run requires framework to be specified when multiple are present

[NTaylorMullen]

Given a project with multiple Target Frameworks, i.e. net451;netcoreapp1.1 dotnet run should behave like it used to in project.json land. At a glance it looks like the old world prioritizes the netcoreapp tfm.

This is how it behaves today:

dotnet run
Unable to run your project.
Please ensure you have a runnable project type and ensure 'dotnet run' supports this project.
The current OutputType is 'Exe'.

[dsplaisted]

The dotnet run command evaluates the MSBuild project and gets the value of the RunCommand property. For a cross-targeting project, this property will only be set in the inner build, not the outer build. I don't think there's a good way for us to have the run properties set to reasonable values at evaluation time in the .NET SDK.

Could the dotnet run command instead read the value of the TargetFrameworks property if RunCommand is not set and the framework wasn't specified on the command line? Then it could choose from the available target frameworks and re-query the value of the RunCommand property when TargetFramework is set to the one it chooses.

@piotrpMSFT @livarcocc

[TheRealPiotrP]

Moved to CLI repo