A .NET Standard server-side implementation of Language Server Protocol 2.0/3.x infrastructure library.
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NuGet version (CXuesong.LanguageServer.VsCode) Gitter

A .NET server-side implementation of Language Server Protocol infrastructure library for VSCode, and hopefully, might also be used with other IDEs that support Language Server Protocol. It supports LSP 2.0 and should support LSP 3.x (if not, please open an issue; thanks).

Screenshot of DemoLanguageServer

Based on CXuesong/JsonRpc.Standard, this .NET Standard library intends to provide basic interfaces and data structures so that you can write a language server in C#, build it on .NET Core and, with the help of the client-side code of Microsoft/vscode-languageserver-node, use it in VSCode.

For an actual (WIP) Wikitext language server based on this library, please take a look at CXuesong/MwLanguageServer.

The library is now available on NuGet. To install the package, run the following command in the Package Manager Console

Install-Package CXuesong.LanguageServer.VsCode -Pre

To set up the demo

You may need Visual Studio 2017 to build the demo.

  1. Open DemoLanguageServer in VS, choose Debug profile, and build the project.
  2. Open Client\VsCode folder in VSCode.
  3. Run npm install in the terminal.
  4. Press F5 and a new VSCode window (Extension Development Host) should show.
  5. Open a folder in the new VSCode window, and create a new file.
  6. Change the file language to Demo Language
  7. Then your editor will work as shown in the screenshot. Enter .net core in the editor and see what happens.

To debug the server application, you may wish to turn WAIT_FOR_DEBUGGER conditional switch on in DemoLanguageServer/Program.cs. After starting up the Extension Development Host, and activating the language server, you may attach VS Debugger to dotnet process and go on debugging.

You may also set the default value of demoLanguageServer.trace.server to "messages" in package.json to make language client show more debugging information.


  • Though it's not mentioned in MS's official LSP documentation, by default VsCode uses stdin/stdout as JSON RPC transportation channel; thus it's important you SHOULD NOT read from/write to the console from your own code as long as the connection has been established, to avoid interfering the JSON RPC communication.
  • If you are using the LSP client library from vscode-languageserver-node, other transportation channels, such as named pipe (Windows) or Unix domain socket (Linux/MacOS) is possible via client-side configuration; though you will need to write your own server-side implementation.
  • It's worthwhile to be noted that Unix domain socket has been introduced since Windows 10 Build 17063. However, there is currently no means to set up a Unix domain socket client in Node.JS on Windows. Thus it seems that, up till now, we still cannot use Unix domain socket as JSON RPC as transportation channel on Windows. See the tracking issue: CXuesong/JsonRpc.Standard#4.