You probably talking about WinApi methods in meaning of word NativeMethods.
If it's true, you must look forward to use P/Invoke in .NET enviroment.
For example calling of method GetDC from User32.dll could be declared in next format:
[DllImport("user32.dll")]
private static extern IntPtr GetDC(IntPtr hWnd);
Take a closer look to
P\Invoke
Good luck.