treeview的使用

private void Form1_Load(object sender, EventArgs e)
     {
            SqlConnection con = new SqlConnection("server=.;database=electcourses;Integrated Security=SSPI;");
            con.Open();

            string str = "select * from Departments";
            SqlCommand cmd = new SqlCommand(str, con);

            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = new SqlCommand(str, con);

            DataSet ds = new DataSet()；
            da.Fill(ds, "Departments");

            int myCount = ds.Tables["Departments"].Rows.Count;

            for (int i = 0; i < myCount; i++)
            {
             string DepartmentName = ds.Tables["departments"].Rows[i][1].ToString();
               int DepartmentID = int.Parse(ds.Tables["departments"].Rows[i][0].ToString());//表关联 关联子节点

                TreeNode CRoot = new TreeNode(DepartmentName);      //2003不为 TreeNode          
                treeView1.Nodes.Add(CRoot);

                AddDirectories(CRoot, DepartmentID);//调用添加子节点方法AddDirectories
            }
        }

        private void AddDirectories(TreeNode node, int departmentid)//子节点方法
        {
            SqlConnection con = new SqlConnection("server=.;database=electcourses;Integrated Security=SSPI;");
            con.Open();

            string str = "select * from Courses where DepartmentID = " + departmentid.ToString();
            SqlCommand cmd = new SqlCommand(str, con);

            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = new SqlCommand(str, con);

            DataSet ds = new DataSet();
            da.Fill(ds, "Courses");          

            int myCount = ds.Tables["courses"].Rows.Count;
            for (int i = 0; i < myCount; i++)
            {
                string CourseName = ds.Tables["courses"].Rows[i][1].ToString();
                node.Nodes.Add(new TreeNode(CourseName));
            }           
        }                                                                                                           //winform 2005环境