[DllImport("user32.dll", EntryPoint = "SetWindowPos",CharSet = CharSet.Auto)]        static extern bool SetWindowPos(        IntPtr hWnd,        IntPtr hWndInsertAfter,        int X,        int Y,        int cx,        int cy,        uint uFlags        );        static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);        static readonly IntPtr HWND_NOTOPMOST = new IntPtr(-2);        static readonly IntPtr HWND_TOP = new IntPtr(0);        const UInt32 SWP_NOSIZE = 0x0001;        const UInt32 SWP_NOMOVE = 0x0002;        const UInt32 SWP_NOZORDER = 0x0004;        const UInt32 SWP_NOREDRAW = 0x0008;        const UInt32 SWP_NOACTIVATE = 0x0010;        const UInt32 SWP_FRAMECHANGED = 0x0020;        const UInt32 SWP_SHOWWINDOW = 0x0040;        const UInt32 SWP_HIDEWINDOW = 0x0080;        const UInt32 SWP_NOCOPYBITS = 0x0100;        const UInt32 SWP_NOOWNERZORDER = 0x0200;        const UInt32 SWP_NOSENDCHANGING = 0x0400;        const UInt32 TOPMOST_FLAGS = SWP_NOMOVE | SWP_NOSIZE;        private void button1_Click(object sender, EventArgs e)        {            Process process = Process.Start("rundll32.exe",@"C:\WINDOWS\system32\shimgvw.dll,ImageView_Fullscreen d:\1.jpg");                        IntPtr str = process.Handle;            SetWindowPos(this.Handle, HWND_NOTOPMOST, 0, 0, 0, 0, 1 | 2); //最后参数也有用1 | 4        }