.NET Core and Mono open source frameworks, and available IDEs.
.NET Core is still work in progress. The download location below contains packages that do not meet the official Fedora requirements yet (such as using prebuilt tools to build the source) but are free.
To enable the .NET SIG’s copr repository:
$ sudo dnf copr enable @dotnet-sig/dotnet
.NET Core SDK will enable building and publishing C# source code.
$ sudo dnf install dotnet-sdk-2.0
You can install runtime only, if you are just deploying already prebuilt application.
$ sudo dnf install dotnet-runtime-2.0
.NET Core packages built by Microsoft contain some proprietary libraries of the .NET Framework.