Did you resolved?
you must use :
using System.Runtime.InteropServices;
and declare :
[DllImport("user32.dll")]
static extern IntPtr SetCapture(long hWnd);
[DllImport("user32.dll")]
static extern long ReleaseCapture();
inside class declaration, where you will use or use like
GenericClass.SetCapture(Control.Handle)
if used as shared function (must be public ofcourse) and use like you write above.
Regards!