asp.net 下拉列表无级数据绑定实现代码

private string toadd = "├".<BR><BR>private void GetArticleCategory(string pid) 
{ 
SqlConnection conn = new SqlConnection("server=.;database=test;uid=sa;pwd=;"); 
string sql = "select Articlesgroup_id,Groupname from Articlesgroup where Articlesgroup_parent_id=@pid order by Groupname"; 
SqlCommand cmd = new SqlCommand(sql, conn); 
SqlParameter Pid = new SqlParameter("@pid", SqlDbType.Int); 
Pid.Value = pid; 
cmd.Parameters.Add(Pid); 
conn.Open(); 
SqlDataReader sdr = cmd.ExecuteReader(); 
while (sdr.Read()) 
{ 
this.DropDownList1.Items.Add(new ListItem(toadd + " " + sdr[1].ToString(), sdr[0].ToString())); 
toadd += "─┴"; 
this.GetArticleCategory(sdr[0].ToString()); 
toadd = toadd.Substring(0, toadd.Length - 2); 
} 
sdr.Close(); 
conn.Close(); 
}

protected void Page_Load(object sender, EventArgs e) 
{ 
this.keyword.Attributes.Add("onfocus","if( this.value=='key key key') {this.value='' };"); 
if (!Page.IsPostBack) 
{ 
this.GetArticleCategory("0"); 
} 
this.DropDownList1.Items.Insert(0, new ListItem("Search All", "all")); 
}