Code
 public static void TreeBindMethod(TreeView tvFile,string target)
        {
            tvFile.Nodes.Clear();
            TreeNode rootNode = new TreeNode("文件管理", "0", "~/Images/file/folder.gif","FileMain.aspx?id=0","");
            tvFile.Nodes.Add(rootNode);
            IList<FileInfo> list = FileInfoService.GetAllEntities().Where(c=>c.IsDelete==false).ToList();
            var query = list.Where(c => c.ParentId == 0).Select(c => c).ToList();
            foreach (FileInfo file in query)
            {
                TreeNode node = GetFileTree(out target, file);
                AddChildTree(list, file, target, node);
                AddTreeMethod(rootNode, node);
            }
        }

private static string filename;
        private static TreeNode GetFileTree(out string target, FileInfo file)
        {

TreeNode node = new TreeNode();
            if (file.FileName.Length > 8)
            {
                filename = file.FileName.Substring(0, 7) + "";
            }
            else {
                filename = file.FileName;
            }
            node.Text = filename;
            node.Value = file.Id.ToString();
            node.ImageUrl = file.FileType.FileTypeImage;
            node.NavigateUrl = string.Format("FileMain.aspx?Id={0}",file.Id);
            target = file.FilePath;
            return node;
        }

private static void AddChildTree(IList<FileInfo> list, FileInfo file,string target, TreeNode fatherNode)
        {
            int id = file.Id;
            var childquery = list.Where(c => c.ParentId == id).ToList();
            foreach (FileInfo childfile in childquery)
            {
                TreeNode childnode = new TreeNode();
                childnode.Text = childfile.FileName;
                childnode.ImageUrl = childfile.FileType.FileTypeImage;
                childnode.NavigateUrl = string.Format("FileMain.aspx?Id={0}", childfile.Id);
                target = childfile.FilePath;
//这里调用了自己，就是递归算法，遍历了树所有节点
                AddChildTree(list, childfile, target, childnode);
                AddTreeMethod(fatherNode, childnode);
            }
        }

private static void AddTreeMethod(TreeNode fatherNode, TreeNode childnode)
        {
            fatherNode.ChildNodes.Add(childnode);
        }
//当然，可以设置一个int depth=0;的参数，在递归算法前，if(depth++>4 yield break;来设置递归深度