用递归在Dropdownlist中显示树状结构

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建立一个aspx页面，copy如下代码
html代码

<HTML>

<HEAD>

<title>WebForm9</title>

</HEAD>

<body>

<asp:DropDownList id="Dropdownlist3" runat="server" Width="352px"></asp:DropDownList></form>

</body>

</HTML>

cs代码

public class WebForm3 : System.Web.UI.Page

{

protected System.Web.UI.WebControls.DropDownList Dropdownlist3;

private void Page_Load(object sender, System.EventArgs e)

{

DataTable dt = GetData();

BindData(dt,0);

}

private void BindData(DataTable dt,int id)

{

DataView dv = new DataView(dt);

dv.RowFilter = "parentid = " + id.ToString();

int m=0;

foreach(DataRowView drv in dv)

{

m++;

string blank="";

if(id!=0)

{

for(int i=0;i<m;i++)

{

blank+="空格";

}

ListItem li=new ListItem();

li.Text=blank+drv["id"].ToString()+drv["name"].ToString();

li.Value=drv["id"].ToString();

this.Dropdownlist3.Items.Add(li);

BindData(dt,Convert.ToInt32(drv["id"]));

}

GetData#region GetData

private DataTable GetData()

{

DataTable dt;

dt = new DataTable();

dt.Columns.Add("id");

dt.Columns.Add("parentid");

dt.Columns.Add("name");

DataRow dr;

dr = dt.NewRow();

dr["id"] = "1";

dr["parentid"] = "0";

dr["name"] = "a";

dt.Rows.Add(dr);

dr = dt.NewRow();

dr["id"] = "2";

dr["parentid"] = "1";

dr["name"] = "b";

dt.Rows.Add(dr);

dr = dt.NewRow();

dr["id"] = "3";

dr["parentid"] = "1";

dr["name"] = "c";

dt.Rows.Add(dr);

dr = dt.NewRow();

dr["id"] = "4";

dr["parentid"] = "2";

dr["name"] = "d";

dt.Rows.Add(dr);

dr = dt.NewRow();

dr["id"] = "5";

dr["parentid"] = "2";

dr["name"] = "e";

dt.Rows.Add(dr);

dr = dt.NewRow();

dr["id"] = "6";

dr["parentid"] = "3";

dr["name"] = "f";

dt.Rows.Add(dr);

return dt;

}

#endregion

Web Form Designer generated code

}