The .NET scripting backend uses Microsoft’s .NET to power scripting. Universal Windows Platform uses a subset of .NET 4.5. This is due to Windows Store certification requirements. This means that the platform has some incompatibilities compared to other platforms, such as a different plugin model and many missing types.
Note: The .NET scripting backend is deprecated and will be removed in a future release of Unity. We recommend switching to the IL2CPP scripting backend.