I use F# Interactive every day, so I like launching it from cmd, not just Visual Studio and Visual Studio Code. To do that, I have an environment variable called FSHARPINSTALLDIR in my PATH that points to C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\CommonExtensions\Microsoft\FSharp. This allows me to simply type fsi to launch F# interactive.
Where is C# Interactive installed so I can do the same thing?