C#使用前序遍历、中序遍历和后序遍历打印二叉树的方法

public class BinaryTreeNode
{
 public BinaryTreeNode Left { get; set; }
 public BinaryTreeNode Right { get; set; }
 public int Data { get; set; }
 public BinaryTreeNode(int data)
 {
  this.Data = data;
 }
}
public enum TreeTraversal
{
  PREORDER,
  INORDER,
  POSTORDER
}
public void PrintTree(BinaryTreeNode root, TreeTraversal treeTraversal)
{
  Action<int> printValue = delegate(int v)
  {
   Console.Write(v + " ");
  };
  switch (treeTraversal)
  {
   case TreeTraversal.PREORDER:
    PreOrderTraversal(printValue, root);
    break;
   case TreeTraversal.INORDER:
    InOrderTraversal(printValue, root);
    break;
   case TreeTraversal.POSTORDER:
    PostOrderTraversal(printValue, root);
    break;
   default: break;
  }
}
public void PreOrderTraversal(Action<int> action, BinaryTreeNode root)
{
  if (root == null)
   return;
  action(root.Data);
  PreOrderTraversal(action, root.Left);
  PreOrderTraversal(action, root.Right);
}
public void InOrderTraversal(Action<int> action, BinaryTreeNode root)
{
  if (root == null)
   return;
  InOrderTraversal(action, root.Left);
  action(root.Data);
  InOrderTraversal(action, root.Right);
}
public void PostOrderTraversal(Action<int> action, BinaryTreeNode root)
{
  if (root == null)
   return;
  PostOrderTraversal(action, root.Left);
  PostOrderTraversal(action, root.Right);
  action(root.Data);
}