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private const int GWL_EXSTYLE = -20;

        private const int WS_EX_NOACTIVATE = 0x08000000;

        [DllImport("user32.dll")]

        public static extern IntPtr SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

        [DllImport("user32.dll")]

        public static extern int GetWindowLong(IntPtr hWnd, int nIndex);

        protected override void OnSourceInitialized(EventArgs e)

        {

            base.OnSourceInitialized(e);

            WindowInteropHelper helper = new WindowInteropHelper(this);

            IntPtr ip = SetWindowLong(helper.Handle, GWL_EXSTYLE,

                GetWindowLong(helper.Handle, GWL_EXSTYLE) | WS_EX_NOACTIVATE);

        }