System.Runtime.InteropServices.CallingConvention enum specifies a calling and is used (for example? or exclusively?) in the field → CallingConvention of the System.Runtime.InteropServices.DllImportAttribute class. Cdecl
FastCall (not supported)
StdCall
ThisCall
Winapi (which uses the default calling convention of the respective platform: Stdcall on 32-bit Windows and Cdecl on 32-bit Linux)