How I Fixed the ‘Cannot Activate C# Dev Kit’ Dependency Error in Cursor IDE

I was excited to start my C# projects in Cursor IDE, but hit a frustrating roadblock. Every time I tried opening a project, an error popped up about the C# Dev Kit extension failing to activate. After hours of trial and error, I finally solved it. Here’s how I fixed it step by step.

The Initial Dependency Error

Installing the C# Dev Kit in Cursor kept throwing this log error: ‘Error: Cannot activate the ‘C# Dev Kit’ extension because it depends on unknown extension ‘ms-dotnettools.csharp’’. Uninstalling and reinstalling changed nothing. My projects remained completely stuck.

The Simple Switch That Fixed C# Support

Turns out the core problem was straightforward. The C# Dev Kit relies on Microsoft’s ‘ms-dotnettools.csharp’, which doesn’t work in Cursor. Here’s what cleared the error:

• First, I completely removed the C# Dev Kit extension.
• Then, I reloaded the Cursor window.
• Finally, I installed the ‘Anysphere C#’ extension instead.

That instantly fixed my C# projects. No more activation warnings – just clean coding.

When F# Support Broke Next

Just when I thought everything was working, my F# projects crashed. The Ionide extension needed the original C# setup. Errors like ‘Cannot activate the ‘Ionide for F#’ extension because it depends on the ‘C#’ extension from ‘Anysphere’’ appeared. Confusing, since Anysphere C# was already installed.

My Workaround for Restoring F# Functionality

To fix F# support, I tested two community solutions. Here’s what did the trick:

• Option 1: Install the Forked Ionide Extension – The ‘Anysphere Ionide-fsharp’ version from the marketplace often worked. When it failed with a ‘couldn’t resolve plugin path’ error, I used plan B.
• Option 2: Patch the Original Extension – I installed the official ‘ionide.ionide-fsharp’ extension, then edited its package.json file. Simply moved the C# dependency from ‘extensionDependencies’ to ‘extensionPack’. Like this:
  "extensionDependencies": ["anysphere.csharp"] became "extensionPack": ["anysphere.csharp"]

After patching and reloading Cursor, F# projects ran perfectly again.

Extension dependencies in Cursor can be tricky, but don’t give up. While waiting for the official fix in the next update, these workarounds keep my coding sessions interruption-free.