How to: Iterate through nodes and collapse specific nodes

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));

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))