ASPNET树形级联

<asp:TreeView ID="tvwChar" runat="server" ExpandDepth="0" OnSelectedNodeChanged="tvwChar_SelectedNodeChanged">
</asp:TreeView>

#region 绑定树操作
private void BindTree()
{
sql = "select id,char_name,char_id from L_Char where char_id=0 and marks=1";
table = DbHelperSQL.Query(sql).Tables[0];
if (table.Rows.Count > 0)
{
for (int i = 0; i < table.Rows.Count; i++)
{
TreeNode tn = new TreeNode();
tn.Text = table.Rows[i]["char_name"].ToString();
tn.Value =  table.Rows[i]["id"].ToString();
tvwChar.Nodes.Add(tn);
sql = "select id,char_name,char_id from L_Char where char_id='" + Convert.ToInt32(table.Rows[i]["id"].ToString()) + "' and marks=1";
DataTable dt = DbHelperSQL.Query(sql).Tables[0];
if (dt.Rows.Count > 0)
{
AddChild(tn, dt);
}
}
}
}
#endregion

#region 添加子节点
/// <summary>
///
/// </summary>
/// <param name="tn"></param>
/// <param name="dt"></param>
private void AddChild(TreeNode tn, DataTable dt)
{
for (int i = 0; i < dt.Rows.Count; i++)
{
TreeNode node = new TreeNode(dt.Rows[i]["char_name"].ToString(), dt.Rows[i]["id"].ToString());
tn.ChildNodes.Add(node);
sql = "select id,char_name,char_id from L_Char where char_id='" + Convert.ToInt32(dt.Rows[i]["id"].ToString()) + "' and marks=1";
DataTable table1 = DbHelperSQL.Query(sql).Tables[0];
if (table1.Rows.Count > 0)
{
AddChild(node, table1);
}
}
}
#endregion

protected void tvwChar_SelectedNodeChanged(object sender, EventArgs e)
    {
        
        txtParentName.Text = tvwChar.SelectedNode.Text;
        hid_Tree_ID.Value = tvwChar.SelectedNode.Value;
    }