为什么返回值TreeNode类型的函数返回值返回不了

Question

代码如下：
private TreeNode GetAllNode(TreeNodeCollection tnc)
        {
            foreach (TreeNode tn in tnc)
            {
                if (tn.Nodes.Count != 0)
                {
                    GetAllNode(tn.Nodes);
                }
                if (tn.Text == this.toolStripTextBox1.Text)
                {
                    return tn;
                }
            }
        }错误 1 “GPSSearch.blacklist.GetAllNode(System.Windows.Forms.TreeNodeCollection)”: 并非所有的代码路径都返回值 D:\GPSSearch\GPSSearch\blacklist.cs 311 25 GPSSearch

Answer 1

if   (tn.Nodes.Count   !=   0)
                                {
                                        GetAllNode(tn.Nodes);
                                }
                                if   (tn.Text   ==   this.toolStripTextBox1.Text)
                                {
                                        return   tn;
                                } 
如果两个IF都不成立，就没有返回值了， 所以报错

Answer 2

private   TreeNode   GetAllNode(TreeNodeCollection   tnc) 
                { 
                        foreach   (TreeNode   tn   in   tnc) 
                        { 
                                if   (tn.Nodes.Count   !=   0) 
                                { 
                                        GetAllNode(tn.Nodes); 
                                } 
                                else if   (tn.Text   ==   this.toolStripTextBox1.Text) 
                                { 
                                        return   tn; 
                                } 
                        } 
                } 

Answer 3

就是说你的代码不一定会返回值
你只要在最后一行加上"return null;"即可