How to: Iterate through nodes and collapse specific nodes

• Nov 13, 2018
• 2 minutes to read

The following example shows how to create an operation class that will collapse all the nodes which do not contain the specified node as their child. Only the node’s parents will be expanded as a result.

The operation class accepts the node as its constructor parameter and stores it in an internal variable. The Execute method checks whether the processed node contains the specified node as a child. If not, the processed node is collapsed. The operation class also overrides the TreeListOperation.NeedsFullIteration property to process only the nodes that have children. This provides performance benefits when working with large and complex node structures.

The image below shows the Tree List before and after executing the sample code:

C#

using DevExpress.XtraTreeList.Nodes;
using DevExpress.XtraTreeList.Nodes.Operations;

public class CollapseExceptSpecifiedOperation : TreeListOperation {
   TreeListNode visibleNode;
   public CollapseExceptSpecifiedOperation(TreeListNode visibleNode) : base() {
      this.visibleNode = visibleNode;
   }
   public override void Execute(TreeListNode node) {
      if (!visibleNode.HasAsParent(node))
         node.Expanded = false;
   }
   public override bool NeedsFullIteration { get { return false; } }
}

//...

treeList1.NodesIterator.DoOperation(new CollapseExceptSpecifiedOperation(treeList1.FocusedNode));

VB.NET

Imports DevExpress.XtraTreeList.Nodes
Imports DevExpress.XtraTreeList.Nodes.Operations

Public Class CollapseExceptSpecifiedOperation
    Inherits TreeListOperation
    Private visibleNode As TreeListNode

    Public Sub New(ByVal visibleNode As TreeListNode)
        Me.visibleNode = visibleNode
    End Sub 'New

    Public Overrides Sub Execute(ByVal node As TreeListNode)
        If Not visibleNode.HasAsParent(node) Then
            node.Expanded = False
        End If
    End Sub 'Execute

    Public Overrides ReadOnly Property NeedsFullIteration() As Boolean
        Get
            Return False
        End Get
    End Property
End Class

'...

TreeList1.NodesIterator.DoOperation(New CollapseExceptSpecifiedOperation(TreeList1.FocusedNode))