Having issues regarding C# Dev Kit

Bug Reports
1

I am having issues trying to open C# projects in Cursor.
After installing all the needed extesions, it keeps showing this message and nothing works.

I have already tried unistall and install again.

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2025-05-20 18:37:54.698 [error] Error: Cannot activate the ‘C# Dev Kit’ extension because it depends on unknown extension ‘ms-dotnettools.csharp’
at iK.j (file:///c:/Users/myuser/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:135:3203)
at file:///c:/Users/myuser/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:135:2390
at Array.map ()
at iK.h (file:///c:/Users/myuser/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:135:2378)
at iK.activateById (file:///c:/Users/myuser/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:135:2290)
at $oe.bb (file:///c:/Users/myuser/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:139:10881)
at $oe.$activate (file:///c:/Users/myuser/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:139:22648)

1 Like
2

@contibru same here
I sent support email for cursor.

from what i saw in the logs, it looks like a mirror problem.
[warning] Error getting latest version of the extension anysphere.csharp 404

3

Hi! Please install the 2nd extension (Anysphere C#); the C# Dev Kit is unsupported as it will link to the Microsoft C# extension, which is not available.

Please uninstall the C# Dev Kit extension, reload the window, and then install Anysphere C#.

4

C# Anysphere makes C# work, but now the F# Ionide extension breaks as it depends on the C# dev extension:

Cannot activate the ‘Ionide for F#’ extension because it depends on the ‘C#’ extension from ‘Anysphere’, which is not installed. Would you like to install the extension and reload the window?

As you can see, somehow the dependency automatically switched to Anysphere over the official C# dev extension, but nonetheless it can’t find it even when installed. And I can’t use the official C# dev extension with Anysphere side by side either.

1 Like
6

I am also now unable to use Ionide for F# support because it depends on the C# extension. As BrunoZ mentioned, it looks like it is trying to map to the new extension but failing.

8

Thanks, this solved the issue.

10

@BrunoZ @Ryan-Palmer thanks for flagging this issue. We forked and published the F# extension that doesn’t depend on the MS C# extension. It is available in the extension marketplace – attaching a screenshot:

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2 Likes
11

@ravirahman Thank you for responding so quickly. Unfortunately the plugin installs but fails to start up. I’ve tried reinstalling / restarting etc etc. I also uninstalled all the MS plugins and the official Ionide before I started to avoid conflicts:

2025-05-29 13:17:17.181 [info] ExtensionService#_doActivateExtension anysphere.Ionide-fsharp, startup: false, activationEvent: 'onLanguage:fsharp'
2025-05-29 13:17:17.211 [error] Activating extension anysphere.Ionide-fsharp failed due to an error:
2025-05-29 13:17:17.211 [error] Error: couldn't resolve plugin path
	at ■■ (c:\Users\Ryan\.cursor\extensions\anysphere.ionide-fsharp-7.25.10\fsharp.js:2:656561)
	at c:\Users\Ryan\.cursor\extensions\anysphere.ionide-fsharp-7.25.10\fsharp.js:2:746416
	at c:\Users\Ryan\.cursor\extensions\anysphere.ionide-fsharp-7.25.10\fsharp.js:2:845262
	at Object.<anonymous> (c:\Users\Ryan\.cursor\extensions\anysphere.ionide-fsharp-7.25.10\fsharp.js:2:845283)
	at Module._compile (node:internal/modules/cjs/loader:1484:14)
	at Module._extensions..js (node:internal/modules/cjs/loader:1564:10)
	at Module.load (node:internal/modules/cjs/loader:1295:32)
	at Module._load (node:internal/modules/cjs/loader:1111:12)
	at c._load (node:electron/js2c/node_init:2:16955)
	at i._load (file:///c:/Users/Ryan/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:195:10980)
	at t._load (file:///c:/Users/Ryan/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:187:23640)
	at s._load (file:///c:/Users/Ryan/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:179:21717)
	at Module.require (node:internal/modules/cjs/loader:1318:19)
	at require (node:internal/modules/helpers:179:18)
	at Joe.yb (file:///c:/Users/Ryan/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:187:25336)
	at async Promise.all (index 0)
13

Hi Ryan, thanks for sharing this new issue. Let me look more into what is happening here.

1 Like
14

I second @Ryan-Palmer’s issue. Except that in my case the Anysphere F# extension doesn’t have any Output (although the Ionide output tab does exist!).

The original Ionide extension in VS Code successfully starts up with:

[14:42:47 DEBUG] [LanguageService] FSAC (NETCORE): 'c:\Users\Bruno\.vscode\extensions\ionide.ionide-fsharp-7.25.10\bin\net9.0\fsautocomplete.dll'
[14:42:47 DEBUG] [LanguageService] F# language server options: % {
  command: 'C:\\Program Files\\dotnet\\dotnet.exe',
  args: [
    'c:\\Users\\Bruno\\.vscode\\extensions\\ionide.ionide-fsharp-7.25.10\\bin\\net9.0\\fsautocomplete.dll',
    '--state-directory',
    'c:\\Users\\Bruno\\AppData\\Roaming\\Code\\User\\workspaceStorage\\ee7cea87989624970385d0fda5445ef5\\Ionide.Ionide-fsharp'
  ],
  options: {
    env: {
       ...
    }
  }
}
[14:42:49 DEBUG] [Main] Activating features

Also how can you be so quick in releasing this. It was just 14 hours!

1 Like
15

@BrunoZ I got that output from the Extensions console rather than Ionide’s :slight_smile:

17

Hi all – we will have a permanent fix for this in the next update to the Cursor client.

In the meantime, could you install the original ionide.ionide-fsharp extension, and then monkeypatch its package.json to move the C# dependency to the “extensionPack” section from the “extensionDependencies”? See After installing the 'C/C++' extension from Anysphere, 'PlatformIO IDE' is not activated - #14 by JoergSH as a guide.

2 Likes