I've generated a .NETCore project using the Yeoman CLI tool on my Mac. I'm able to run the project using Visual Studio Code. However I want to be able to open and run the project with either Xamarin Studio or Visual Studio Preview. Is this possible? Both IDEs seem to require an .sln file, however the Yeoman generated project doesn't provide one.
To be correct, both IDEs supports .csproj file, not project.json, that was announced with latest .NET Core Tools. What you may try to do is to migrate your project.json using the dotnet migrate command:
dotnet-migrate -- Migrates a Preview 2 .NET Core project to Preview 3 .NET Core project