There is only one file type that uses the .WINMD extension:
Windows Metadata File
File created using the Microsoft Interface Definition Language (MIDL); contains metadata that represents the API for customized Windows Runtime components; written in the DLL file format but does not have to contain code like traditional .DLL files; its format is used by the .NET framework.
To create the WINMD file, use the MIDLRT compiler.
WINMD files are located in C:\Windows\System32\WinMetadata\.
|Microsoft Visual Studio||Commercial|
Updated: September 6, 2017