.NET mappings of Windows Runtime types in UWP apps
This article lists the mappings that .NET makes between Windows Runtime (WinRT) types and .NET types in Universal Windows Platform (UWP) apps written with managed code. In these apps, Visual Studio IntelliSense shows the .NET type instead of the WinRT type. For example, if a WinRT method takes a parameter of type IVector<string>, then IntelliSense shows a parameter of type IList<string>. Similarly, in a Windows Runtime component written with managed code, you use the .NET type in member signatures. When the Windows Runtime Metadata Export Tool (Winmdexp.exe) generates your Windows Runtime component, the .NET type is translated into the corresponding WinRT type.
Most of the types that have the same namespace name and type name in both WinRT and .NET are structures (or types associated with structures, such as enumerations). In WinRT, structures have no members other than fields, and require helper types, which .NET hides. The .NET versions of these structures have properties and methods that provide the functionality of the hidden helper types.