Windows Forms is originally a class library that is part of the .NET Framework and is, in fact, a wrapper over the Win API. Supported languages are C#, C++, VB and other .NET languages. Therefore, Visual Studio does not support the C form designer or any C support for Windows Forms. For C, you can use the low-level Win API to create GUI applications. However, you have to do everything directly in C code, placing each interface element manually, setting everything (including the ability to close the window, resize it, etc.), and this can all take a lot of time and lines of code.
And therefore, I recommend using existing GUI libraries like GTK, Tk, IUP, etc.
