Prevent Maximize and Restore on RadWindow TitleBar Double Click

Updated on Feb 9, 2026

Environment

Product	Window for UI for WPF
Version	2025.3.813

Description

How to prevent the default double-click behavior on the titlebar (header) of a RadWindow or a native WPF Window.

By default, double-clicking on the header causes the window to switch states from maximized to restored or vice versa.

Solution

To prevent the default behavior, you can use interop methods to remove the maximize box of the host window of the RadWindow control. Then, you can add a procedure hook and prevent the button double click on the titlebar or on the top resize handle of the window.

The example below checks for the HTTOP and HTCAPTION hit test messages. You an read about these in the official win32 docs.

csharp

// The purpose of this method is to demonstrate one way to subscribe for the HostCreated event of RadWindow.
// This setup may vary based on your exact implementation and usage of the control.
public void ShowWindow()
{
	var window = new RadWindow();
	window.HostCreated += RadWindow_HostCreated;
	window.Show();
}

private const int GWL_STYLE = -16;
private const int WS_MAXIMIZEBOX = 0x10000;
private const int WM_NCLBUTTONDBLCLK = 0x00A3;
private const int HTTOP = 12;
private const int HTCAPTION = 2;

[DllImport("user32.dll")]
private static extern int GetWindowLong(IntPtr hWnd, int nIndex);

[DllImport("user32.dll")]
private static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

private void RadWindow_HostCreated(object sender, HostWindowCreatedEventArgs e)
{
	e.HostWindow.SourceInitialized += Window_SourceInitialized;
}

private void Window_SourceInitialized(object sender, EventArgs e)
{
	// Remove maximize box, thus disabling maximize on double click of the titlebar
	IntPtr hwnd = new WindowInteropHelper((Window)sender).Handle;
	var value = GetWindowLong(hwnd, GWL_STYLE);
	SetWindowLong(hwnd, GWL_STYLE, (int)(value & ~WS_MAXIMIZEBOX));

	// Add window procedure hook
	HwndSource source = HwndSource.FromHwnd(hwnd);
	source.AddHook(WndProc);
}

private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
	// Block double-click on top resize border (vertical maximize) and the titlebar
	if (msg == WM_NCLBUTTONDBLCLK && (wParam.ToInt32() == HTTOP || wParam.ToInt32() == HTCAPTION))
	{
		handled = true;
		return IntPtr.Zero;
	}
	return IntPtr.Zero;
}