/// <summary>
 /// 根据ParentId返回对应的版块的集合方法,集合元素是保存版块信息的Category对象 方法
 /// </summary>
 /// <param name="pid">parentid</param>
 /// <returns></returns>
 private List<Category> GetCategoryByParentId(int pid)
 {
     List<Category> list = new List<Category>();
     string sql = "select tId,tName from category where tParentId=@pid";
     using (SqlDataReader reader = SqlHelper.ExecuteSqlDataReader(sql, new SqlParameter("@pid", pid)))
     {
         if (reader.HasRows)
         {
             while (reader.Read())
             {
                 Category c = new Category();
                 c.tId = reader.GetInt32(0);
                 c.tName = reader.GetString(1);
                 list.Add(c);
             }
         }
     }
     return list;
 }
        /// <summary>
        /// treeView子节  菜单点击添加子类别事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void 增加子类ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2();
            f2.ShowDialog();
            Category category = new Category();
            TreeNode node = treeView1.SelectedNode.Nodes.Add(f2.name);
            node.ContextMenuStrip = contextMenuStrip1;//给新节点绑定右键菜单
            //给TreeView增加新类别完成
            //但记得把tid放到新的节点的tag中,而tid是Category表中的主键,要在表中增加这条数据才能获得

            string sql = "insert into Category(tName,tParentId) output inserted.tId values(@name,@parentId)";
            SqlParameter[] parameters = new SqlParameter[]{
                new SqlParameter("@name",f2.name),
                new SqlParameter("@parentId",(int)treeView1.SelectedNode.Tag)
            };
            int tid = (int)SqlHelper.ExecuteScalar(sql, parameters);
            node.Tag = tid;
        }