static extern bool AnimateWindow(IntPtr hwnd, int time, AnimateWindowFlags flags);

Shared Function AnimateWindow(ByVal hwnd As IntPtr, ByVal time As Integer, ByVal flags As AnimateWindowFlags) As Boolean

AnimateWindowFlags should be used for the dwFlags parameter.

Don’t forget to use the AnimateWindowFlags!

AnimateWindow(f2.Handle, 1000, AnimateWindowFlags.AW_VER_NEGATIVE Or AnimateWindowFlags.AW_SLIDE or AnimateWindowFlags.AW_HIDE)

AnimateWindow doesn't actually show the window so make sure you call Show() or set this.Visible = true after calling AnimateWindow

This assumes that the AnimateWindow function is declared inside class User32

AnimateWindow(f2.Handle, 1000, (uint) AnimateWindowFlags.AW_VER_NEGATIVE | (uint) AnimateWindowFlags.AW_SLIDE);

AnimateWindow(f2.Handle, 1000, AnimateWindowFlags.AW_VER_NEGATIVE Or AnimateWindowFlags.AW_SLIDE or AnimateWindowFlags.AW_HIDE)

enum AnimateWindowFlags : uint

public sealed class AnimateWindowFlags

public enum AnimateWindowFlags

    Public Enum AnimateWindowFlags