Clarify use of C# extension without C# Dev Kit

[PyrateAkananto]

In addition to the clarification of the dependency direction mentioned in #6171 I would really appreciate if the description of the C# extension includes even more instructions.

While it is possible to use the C# extension as a standalone extension, we highly recommend using C# Dev Kit.

1. Installing C# Dev Kit will automatically install this extension as a required dependency.
2. ...
3. ...

Please add another list of 1./2./3. instructions how to use this extension without C# Dev Kit!

I assume (but I am not sure) it would use OmniSharp instead, just like version 1 of the extension.

[dibarbet]

It is totally possible to use the C# extension by itself. There are two possible modes that the C# extension runs in when devkit is not installed.

1. Roslyn LSP mode - this is the new default in 2.x.
2. O# mode (via the dotnet.server.useOmnisharp option)

We generally recommend using Roslyn LSP instead of O# mode and should generally work for most modern .net projects. There are a few known parity gaps between Roslyn LSP and O# (see #5736). If you're hitting any of those cases you'll have to switch to O# until we resolve those issues.

Assigning to @mikadumont to see if we need any doc updates.

[PyrateAkananto]

As far as I understand it Roslyn LSP mode is provided by the C# Dev Kit extension. Unfortunately this extension is not open source with a permissive license but brings license terms which I, as an "enterprise" user, currently don't want to accept (because I would have to pay the full price of Visual Studio Professional 2022 to use Visual Studio Code plus C# Dev Kit).

In version 1 of the C# extension OmniSharp was installed by the extension. Is this still the case for version 2 of the C# extension? Or do I have to install OmniSharp myself somehow?

[claytonweaver]

You get the LSP mode with just the standalone C# extension, you don't need the dev kit extension. I use that for work everyday and it works just fine for me.

[juner]

source generator does not work if dotnet.server.useOmnisharp is not used. #6373