下面的示例展示了如何使用 节点迭代器 获取位于指定嵌套层级上的节点数目。 在本示例中，创建了一个用于计算节点数目的 CustomNodeOperation 对象。 这个操作类包含一个内部计数器，每次当位于指定嵌套层级上的节点被访问时，此计数器都会被递增 1。

为了获取位于指定嵌套层级上的节点总数，创建了 CustomNodeOperation 类的一个实例，并传递给 TreeListNodesIterator.DoLocalOperation 方法。 在此方法执行完毕之后，读取 CustomNodeOperation.NodeCount 属性来获得节点数目。

C#CopyCode image复制代码
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)
         nodeCount++;
   }
   public int NodeCount {
      get { return nodeCount; }
   }
}

// ...

CustomNodeOperation operation = new CustomNodeOperation(2);
treeList1.NodesIterator.DoLocalOperation(operation, treeList1.Nodes);
int totalNodesAtSecondLevel = operation.NodeCount;
Visual BasicCopyCode image复制代码
Imports DevExpress.XtraTreeList.Nodes
Imports DevExpress.XtraTreeList.Nodes.Operations

' Declaring the custom operation class.
Class CustomNodeOperation
    Inherits TreeListOperation
    Private level As Integer
    Private nodeCount As Integer

    Public Sub New(ByVal level As Integer)
        Me.level = level
        Me.nodeCount = 0
    End Sub 'New

    Public Overrides Sub Execute(ByVal node As TreeListNode)
        If node.Level = level Then
            nodeCount += 1
        End If
    End Sub 'Execute

    Public ReadOnly Property NodeCount() As Integer
        Get
            Return nodeCount
        End Get
    End Property
End Class

'...

Dim operation As CustomNodeOperation = New CustomNodeOperation(2)
TreeList1.NodesIterator.DoLocalOperation(operation, TreeList1.Nodes)
Dim totalNodesAtSecondLevel As Integer = operation.NodeCount