How to: Iterate through nodes and calculate the number of nodes at a specific level

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The following example shows how to use the Nodes Iterator to obtain the number of nodes which reside on the specified nesting level.

In the example, a CustomNodeOperation object is created that is used to calculate this number. The operation class contains an internal counter that is incremented by one each time a node that resides at the specified nesting level is accessed.

To get the total number of the nodes which reside at the specified nesting level, a CustomNodeOperation instance is created and passed to the TreeListNodesIterator.DoLocalOperation method. After the method has been performed, the CustomNodeOperation.NodeCount property is read to get the number of nodes.

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

// Declaring the custom operation class.
class CustomNodeOperation : TreeListOperation {
   int level;
   int nodeCount;
   public CustomNodeOperation(int level) : base() {
      this.level = level;
      this.nodeCount = 0;
   public override void Execute(TreeListNode node) {
      if(node.Level == level)
   public int NodeCount {
      get { return nodeCount; }

// ...

CustomNodeOperation operation = new CustomNodeOperation(2);
treeList1.NodesIterator.DoLocalOperation(operation, treeList1.Nodes);
int totalNodesAtSecondLevel = operation.NodeCount;