DropDownList无限级分类(灵活控制显示形式)

protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
BindDrpClass();
}
}
//绑定顶级分类
private void BindDrpClass()
{
Bll.Class classSystem = new Bll.Class();
DataTable dt = classSystem.GetClassList("").Tables[0];
ddlClass.Items.Clear();
ddlClass.Items.Add(new ListItem("添加根栏目", "0"));
DataRow[] drs = dt.Select("ParentID= " + 0);
foreach (DataRow dr in drs)
{
string classid = dr["ClassID"].ToString();
string classname = dr["ClassName"].ToString();
//顶级分类显示形式
        classname = "╋" + classname;
ddlClass.Items.Add(new ListItem(classname, classid));
int sonparentid = int.Parse(classid);
string blank = "├";
//递归子分类方法
        BindNode(sonparentid, dt, blank);
}
ddlClass.DataBind();
}
//绑定子分类
private void BindNode(int parentid, DataTable dt, string blank)
{
DataRow[] drs = dt.Select("ParentID= " + parentid);
foreach (DataRow dr in drs)
{
string classid = dr["ClassID"].ToString();
string classname = dr["ClassName"].ToString();
classname = blank + classname;
ddlClass.Items.Add(new ListItem(classname, classid));
int sonparentid = int.Parse(classid);
string blank2 = blank + "─";
BindNode(sonparentid, dt, blank2);
}
}

public DataSet GetClassList(string strWhere)
{
StringBuilder strSql = new StringBuilder();
strSql.Append("select * from tb_Class ");
if (strWhere.Trim() != "")
{
strSql.Append(" where " + strWhere);
}
return SqlHelper.ExecuteDataset(SqlHelper.ConnString, CommandType.Text, strSql.ToString());
}