C#的 foreach in 问题 急

Question

public void getTreeNode(TreeNodeCollection tn, string name)
        {
            //tn2 = null;
            foreach (TreeNode tree_node in tn)
            {
                if (tree_node.Text == name)
                {
                   MessageBox.Show(tree_node.Text);
                   tn2 = tree_node;
                   break;
                }
                    getTreeNode(tree_node.Nodes, name);
            }
        }
问什么会弹两个MessageBox
我用break return都会弹两个 
我想弹出一个后就退出函数 怎么做呢

Answer 1

因为递归的问题，break或return只是退出当前的而不是上级 的
public bool getTreeNode(TreeNodeCollection tn, string name)
        {
            if(getTreeNode(tree_node.Nodes, name)==true)
              return true;
            else
            foreach (TreeNode tree_node in tn)
            {
                if (tree_node.Text == name)
                {
                   MessageBox.Show(tree_node.Text);
                   tn2 = tree_node;
                   return true;
                }
                    
            }
            return false;
        }

Answer 2

你用了递归。
当 Text != name，会进入 getTreeNode(tree_node.Nodes, name)，所以会遇到两个 == name 也是很正常的。会弹两个MessageBox，应该 TreeNodeCollection 中至少有两个Text和name一样。你去看看是不是。

Answer 3

但是用break不能退出循环么。。

Answer 4

 public bool getTreeNode(TreeNodeCollection tn, string name)
        {
           
            foreach (TreeNode tree_node in tn)
            {
                if (getTreeNode(tree_node.Nodes, name) == true)
                    return true;
                if (tree_node.Text == name)
                {
                  MessageBox.Show(tree_node.Text);
                  return true;
                }
                   
            }
            return false;
        }

Answer 5

public void getTreeNode(TreeNodeCollection tn, string name)
        {
            //tn2 = null;
            foreach (TreeNode tree_node in tn)
            {
                if (tree_node.Text == name)
                {
                   MessageBox.Show(tree_node.Text);
                   tn2 = tree_node;
                   return;
                }
                    getTreeNode(tree_node.Nodes, name);
                     return;
            }
        }

Answer 6

但是当符合Text==name出现后 不是break么 break后为什么不退出函数 而是进入getTreeNode(tree_node.Nodes, name)呢

Answer 7

public bool getTreeNode(TreeNodeCollection tn, string name)
        {
            //tn2 = null;
            foreach (TreeNode tree_node in tn)
            {
                if (tree_node.Text == name)
                {
                   MessageBox.Show(tree_node.Text);
                   tn2 = tree_node;
                   return true;
                   //break;
                }
                else
                {
                   getTreeNode(tree_node.Nodes, name);                }
                    
            }
        }