C++/CLI is a Microsoft-specific dialect of C++ which interoperates well with .NET. Originally, it was envisioned as the "most powerful" of .NET languages and included designer support for WinForms applications. However, new development on C++/CLI has all but ceased, and Microsoft now intends that the language only be used in "interop" scenarios:
Interop scenarios that might be complex with P/Invoke can be considerably easier with C++/CLI.
Detailed instructions on getting c++-cli set up or installed.