Building the MahApps.Metro solution - MahApps/MahApps.Metro GitHub Wiki

Quick start for developers

Download the .NET Core 3.1.x SDK and Runtime from here
Make sure you have Visual Studio 2019 16.8.x or higher (Preview) installed (this could also be the Community Edition)
Clone the MahApps.Metro repository. You can also download the repo as zip, but at your own risk.
Open the MahApps.Metro.sln solution from the src folder in Visual Studio 2019
Rebuild and you're done...