Umbraco Add Extension Reference

After you create a new Umbraco backoffice extension, it needs to be wired up as a project reference in your main Umbraco instance or it simply won't load. This automates that tedious step by finding your main .csproj file (the one with the Umbraco.Cms package), calculating the relative path to your extension, and adding the ProjectReference entry in the right spot. It'll also add the extension to your .sln file if you have one, which is optional but makes IDE navigation nicer. The skill handles the annoying edge cases like multiple projects or missing solution files. Beats manually editing XML and getting the relative path wrong, which I've definitely never done three times in a row.

skills.sh installs: 402
GitHub stars: 27
last updated: Aug 21, 2026

View on GitHub

Install

$ npx -y skills add umbraco/umbraco-cms-backoffice-skills --skill umbraco-add-extension-reference --agent claude-code

Installs into .claude/skills of the current project.

Files

Add Extension Reference to Umbraco Instance

What is it?

After creating a new Umbraco backoffice extension project, it must be added as a project reference in the main Umbraco instance's .csproj file. Without this reference, the extension will not be loaded when running the Umbraco site.

If a solution file (.sln) exists, the extension should also be added to it for proper IDE support (Visual Studio, Rider). This is optional - the extension will work without being in the solution.

When to Use

Use this skill after:

Creating a new extension with dotnet new umbraco-extension
Moving or copying an extension project to your solution
Setting up a new extension from the umbraco-backoffice blueprints

Workflow

Step 1: Find the Main Umbraco Project

The main Umbraco instance .csproj file must be discovered dynamically. Search for it using these criteria:

# Find all .csproj files
Glob: **/*.csproj

# Then search for the one containing Umbraco.Cms package reference
Grep: Umbraco\.Cms" Version  (in *.csproj files)

The main Umbraco project will have: