treeview控件使用+连接数据库库

 
//没有理由不坚持，慢慢走吧，后面的路或许很难，别放弃！
private void Form3_Load(object sender, EventArgs e)
        {
          //添加一个根节点
            TreeNode root = new TreeNode("游戏类型");
            treeView1.Nodes.Add(root);
         //在数据库查找需要的类型，生成子节点
            string sql = "select * from Categories";
            DataTable table = DBHelper.Query(sql);
          //循环查找出数据库的类型，生成子节点
            foreach (DataRow row in table.Rows)
            {
                string name = row["Name"].ToString();
               //int类型储存id
                int id = (int)row["ID"];
                TreeNode node = new TreeNode(name);
                node.Tag = id;
               //初始值为0
                root.Tag = 0;
                root.Nodes.Add(node);
            }
         //让treeview试图在界面打开时全部展开
            treeView1.ExpandAll();
        }

       //在点击对应的节点在datagridview的控件中显示相应的试图
        private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)
        {
            int id=(int)(treeView1.SelectedNode.Tag);
            int cateid=id;
            string sql = string.Format("select * from Products where CategoryID='{0}'", cateid);
            dataGridView1.DataSource = DBHelper.Query(sql);
        }
    }
}