The Maya .NET API uses .NET 4.8.
It is generated from the Maya C++ API. The C# classes are proxies for C++ classes.
The .NET SDK class libraries, openmayacs.dll and swigfiles.dll, are located under the bin directory of your Maya installation directory. By default, Maya is installed to C:\Program Files\Autodesk\<maya_version>.
The OpenMaya XML documentation, openmayacs.xml, is located in the same directory, and will be loaded automatically when the class libraries are added to your solution references in Visual Studio. See Compiling the .NET examples for more information.
The .NET examples are located under devkitBase\devkit\dotnet.