给dropdownlist手动添加一列"请选择"(不是从数据库中读取的数据)

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindJueSe();
        }
    }

public void BindJueSe()
    {
        ddljuese.DataSource = DAL.Juese();
        ddljuese.DataValueField = "userrole_id";
        ddljuese.DataTextField = "userrole_name";
        ddljuese.DataBind();
        ddljuese.Items.Insert(0, new ListItem("--请选择--", "0"));   //如果是ddljuese.Items.Insert(0, new ListItem(" "," "));插入空值。
        //或者
        //ListItem it = new ListItem("--请选择--", "0");  
        //ddljuese.Items.Insert(0, it);  
        //或者（这样“请选择会出现在最后一列”）
        //ListItem lt = new ListItem();
        //lt.Text = "--请选择--";
        //lt.Value = "00";
        //lt.Selected = true;
        //ddljuese.Items.Add(lt);
    }