There should be two debug profiles available in VS drop down

Debug profiles

However due to VS 2017 RC4 bug it seems that it's impossible to choose as of 2/19/2017. If you want to change it then please edit the project file (.csproj) and set your order - the first framework moniker is always used. <TargetFrameworks>netcoreapp1.1;net46</TargetFrameworks>