1) Install the C# extension 2) 2.a) DO NOT USE OPEN FILE 2.b) Always use (from the menu), and open the folder containing your sln file (or the folder containing the if you have only one ) 3) To make the extension start and detect C#, either: 3.a) wait for the prompt that will appear on the bottom right of your screen that ask you if you want it to create some files, and say 3.b) Command Palette ( or ) and type 4) you should see a flame on the bar with the Omnisharp logo (see second attached screenshot) 5) it should load to finally say OmniSharp server is running (if not ask for help)