Prevent RadDiagramConnection Point from Delete

Updated on Apr 3, 2026

Environment

Product Version	2019.3.1023
Product	RadDiagram for WPF

Description

How to prevent the RadDiagramConnection point from being deleted.

Solution

To achieve this requirement, you can handle the PreviewMouseLeftButtonDown event of RadDiagram in the situation when Ctrl is pressed, and a RadDiagramConnection point is under the mouse.

Example 1: Prevent RadDiagramConnection Point from Delete

C#

private void Diagram_PreviewMouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
	var selectionService = this.diagram.ServiceLocator.GetService<ISelectionService<IDiagramItem>>() as SelectionService;
	if (KeyboardModifiers.IsControlDown)
	{
		var selectedConnection = selectionService.SelectedConnections.FirstOrDefault();
		if (selectedConnection != null)
		{
			var position = e.GetPosition(this.diagram);
			var transformedPosition = this.diagram.GetTransformedPoint(position);
			var relativePoint = new Point(transformedPosition.X - 5, transformedPosition.Y - 5);
			var rect = new Rect(relativePoint, new Size(10, 10));
			if (selectedConnection.ConnectionPoints.Any(rect.Contains))
			{
				e.Handled = true;
			}
		}
	}
}