Greetings,
As I was experiencing the same issue, I guess I went through all possible reasons why a problem like that may happen and I thought of sharing the fixes with you guys.
First of all make sure to install : .Net “dotnet” version 6, for example : SDK 6.0.309
and .NET Framework 4.7.1 Dev pack, make sure you selected Dev pack and not the Run time.
Reasons : for me I had the version 7.0 and I kept having problems so when I went through the logs I found out that Vs Code was getting Omni sharp updates required for for a dotnet core of 6.0 and not a 7.0.
Second problem that might occur: Let’s say you had the Version 7.0 installed, you uninstalled it and installed the version 6.0 but you kept receiving errors.
reason this problem still occur : in your folder " C:\Program Files\dotnet " You may still have traces of other versions that you may have used before and uninstalled. the folders will still have remains of the uninstalled version but without the dotnet.exe so what happens is that vscode goes to the greater version available, let’s say 7.0 but what happens then is that he doesn’t find the " dotnet.exe" so basically suggestions won’t work even if you install the C# extension.
what you should do at this point : if you know what you are doing, you have to go through each folder and check if there is a remain of a version that you are not using anymore.
if you are someone that doesn’t want to go through that pain. you can uninstall the current version of dotnet you have. go to your program files, then you fill find a remaining folder of dotnet that you don’t want., delete that folder and reinstall the dotnet 6.0 again.
Third reason why you may still experience a problem is dotnet path. in my case I had all these 3 problems and I had to fix them one by one LOL.
so for this last problem : go to start and tape " edit the system environment " then go to Environment variables, in the user Variables check if you have the dotnet path in there, if not just create new name it “DotNet” and for the path set is as " C:\Program Files\dotnet " or wherever you installed dotnet.
by now your problem should be fixed.