public static void GetCheckedNode(TreeNodeCollection tnc)
{
        foreach(TreeNode node in tnc)
        {
            if(node.Checked) 
　　　        {
                MessageBox.Show(node.Text);
            }   
　　          GetCheckedNode(node.Nodes); 
         }
}

------解决方案--------------------
 
C# code
private void button1_Click(object sender, EventArgs e)
        {
            List<TreeNode> t = getchecknode(this.treeView1.Nodes);
            
        }


        private List<TreeNode> getchecknode(TreeNodeCollection nodes)
        {
            List<TreeNode> getnodes = new List<TreeNode>();
            foreach (TreeNode td in nodes)
            {
                if (td.Checked) getnodes.Add(td);
                if(td.Nodes.Count!=0) 
                {
                    getnodes.AddRange(getchecknode(td.Nodes));
                }
            }
            return getnodes;
        }