How to Delete Diagram Shapes with All Related Connections

Environment

Product Version	Product	Author
2022.3.913	RadDiagram for WinForms	Desislava Yordanova

Description

When a shape is selected in RadDiagram and the user hits the Delete key, only the RadDiagramShape is removed. All connections related to the shape remain. This article demonstrates how to delete the connections together with the shape after pressing Delete.

Solution

DiagramInputBehavior is responsible for handling the user's input. Hence, we should create a derivative of DiagramInputBehavior and override its HandleKeyDown. When the Delete key is pressed, all selected shapes are iterated, their connections are removed. In the end, the selected shape is also deleted:

public RadForm1()
{
    InitializeComponent();

    this.radDiagram1.SelectionMode = Telerik.Windows.Diagrams.Core.SelectionMode.Multiple;
    this.radDiagram1.DiagramElement.InputBehavior = new CustomDiagramInputBehavior(this.radDiagram1.DiagramElement);
}

public class CustomDiagramInputBehavior : DiagramInputBehavior
{
    public CustomDiagramInputBehavior(RadDiagramElement diagramElement) : base(diagramElement)
    {
    }

    public override bool HandleKeyDown(KeyEventArgs e)
    {
        if (e.KeyData== Keys.Delete)
        {
            Console.WriteLine(DateTime.Now.ToLongTimeString());
            if (!this.DiagramElement.SelectedItems.Any(d => d.IsInEditMode == true))
            {
                List<RadDiagramShape> shapesToDelete = new List<RadDiagramShape>();
                foreach (RadDiagramItem item in this.DiagramElement.SelectedItems)
                {
                    RadDiagramShape shape = item as RadDiagramShape;
                    if (item == null)
                    {
                        continue;
                    }

                    List<RadDiagramConnection> connectionsToDelete = new List<RadDiagramConnection>();
                    foreach (RadDiagramConnection connection in this.DiagramElement.Connections)
                    {
                        if (connection.Source == shape || connection.Target == shape)
                        {
                            connectionsToDelete.Add(connection);
                        }
                    }
                    while (connectionsToDelete.Count > 0)
                    {
                        this.DiagramElement.Items.Remove(connectionsToDelete.First());
                        connectionsToDelete.RemoveAt(0);
                    }
                    shapesToDelete.Add(shape);
                }
                while (shapesToDelete.Count > 0)
                {
                    this.DiagramElement.Items.Remove(shapesToDelete.First());
                    shapesToDelete.RemoveAt(0);
                }
                return true;
            }

        }
        return base.HandleKeyDown(e);
    }
}

Public Sub New()
    InitializeComponent()
    Me.RadDiagram1.SelectionMode = Telerik.Windows.Diagrams.Core.SelectionMode.Multiple
    Me.RadDiagram1.DiagramElement.InputBehavior = New CustomDiagramInputBehavior(Me.RadDiagram1.DiagramElement)
End Sub

Public Class CustomDiagramInputBehavior
    Inherits DiagramInputBehavior

    Public Sub New(ByVal diagramElement As RadDiagramElement)
        MyBase.New(diagramElement)
    End Sub

    Public Overrides Function HandleKeyDown(ByVal e As KeyEventArgs) As Boolean
        If e.KeyData = Keys.Delete Then
            Console.WriteLine(DateTime.Now.ToLongTimeString())

            If Not Me.DiagramElement.SelectedItems.Any(Function(d) d.IsInEditMode = True) Then
                Dim shapesToDelete As List(Of RadDiagramShape) = New List(Of RadDiagramShape)()

                For Each item As RadDiagramItem In Me.DiagramElement.SelectedItems
                    Dim shape As RadDiagramShape = TryCast(item, RadDiagramShape)

                    If item Is Nothing Then
                        Continue For
                    End If

                    Dim connectionsToDelete As List(Of RadDiagramConnection) = New List(Of RadDiagramConnection)()

                    For Each connection As RadDiagramConnection In Me.DiagramElement.Connections

                        If connection.Source.Equals(shape) OrElse connection.Target.Equals(shape) Then
                            connectionsToDelete.Add(connection)
                        End If
                    Next

                    While connectionsToDelete.Count > 0
                        Me.DiagramElement.Items.Remove(connectionsToDelete.First())
                        connectionsToDelete.RemoveAt(0)
                    End While

                    shapesToDelete.Add(shape)
                Next

                While shapesToDelete.Count > 0
                    Me.DiagramElement.Items.Remove(shapesToDelete.First())
                    shapesToDelete.RemoveAt(0)
                End While

                Return True
            End If
        End If

        Return MyBase.HandleKeyDown(e)
    End Function
End Class