[System.Runtime.InteropServices.DllImport("user32.dll ")]        public static extern int SetWindowLong(IntPtr hWnd, int nIndex, int wndproc);        [System.Runtime.InteropServices.DllImport("user32.dll ")]        public static extern int GetWindowLong(IntPtr hWnd, int nIndex);        public const int GWL_STYLE = -16;        public const int WS_DISABLED = 0x8000000;        public static void SetControlEnabled(Control c, bool enabled)        {            if (enabled)            { SetWindowLong(c.Handle, GWL_STYLE, (~WS_DISABLED) & GetWindowLong(c.Handle, GWL_STYLE)); }            else            { SetWindowLong(c.Handle, GWL_STYLE, WS_DISABLED + GetWindowLong(c.Handle, GWL_STYLE)); }        }        private void button2_Click(object sender, System.EventArgs e)        {            SetControlEnabled(this.button1, false);            this.button1.ForeColor = Color.White;        }