This topic explains how a diagram item is copied when dropped on the diagram surface from the toolbox.
The following topics are prerequisites to understanding this topic:
When the user drags a DiagramItem from the toolbox and drops it on the diagram’s surface or performs a copy-paste operation, the control creates a copy of this item. In addition the following item’s properties are also copied:
DragDropData - this property is copied using "shallow copy" - this process create a reference copies of the same object instance.
Content - this property is copied using "deep copy" - this process create object duplication using reflection by taking the advantage of the Activator.CreateInstance() method which means the duplicated diagram items will have their own instances of the mentioned property’s values. Keep in mind however that bindings and event handlers are not copied.
In certain cases you may need to disable the deep coping of the diagram item’s Content property. To achieve this you need to follow these steps:
Create a custom class which extends from either DiagramNode or DiagramConnection
Override the Clone method
In the new Clone method invoke respectively the CloneDiagramNodeProperties or the CloneDiagramConnectionProperties method
Set the last boolean argument to false
The following code example demonstrate how to prevent coping of the Content property of a DiagramNode:
In C#:
public class CustomDiagramNode : DiagramNode
{
public override DiagramItem Clone()
{
var newCustomDiagramNode = new CustomDiagramNode();
CloneDiagramNodeProperties(this, newCustomDiagramNode, false);
return newCustomDiagramNode;
}
}In VB:
Public Class CustomDiagramNode
Inherits DiagramNode
Public Overrides Function Clone() As DiagramItem
Dim newCustomDiagramNode = New CustomDiagramNode()
CloneDiagramNodeProperties(Me, newCustomDiagramNode, False)
Return newCustomDiagramNode
End Function
End ClassThe following topics provide additional information related to this topic.