public class TreeNode
     
         {      public TreeNode()      {         Children = new List
      
       
        >();      }      public void AddChild(TreeNode
        
          item)      {         item.Parent = this;         Children.Add(item);      }      public List
         
          
           > Children { get; set; } public TreeNode
           
             Parent { get; set; } public T Data { get; set; } public bool IsLeaf { get { return !Children.Any(); } } }