Install .NET on Manjaro

.NET Core
If you only want to run .NET Core managed applications, install the dotnet-runtime package.
To build apps with .NET Core, install dotnet-sdk as well.
Microsoft recommends using Visual Studio Code , their Electron-based FOSS IDE, to build & debug .NET Core apps.

Tip: Add ~/.dotnet/tools to PATH, otherwise dotnet tools with not work from shell.

Mono

Install the mono package.

References
https://wiki.archlinux.org/index.php/.NET_Core
https://wiki.archlinux.org/index.php/Mono