DropDownList 加入行

public void DropDownListInertRow()
    {
        string SqlStr = "select CategoryName from Categories";
        da = new SqlDataAdapter(SqlStr, con);
        da.Fill(ds, "Categories");
        DropDownList4.DataSource = ds.Tables["Categories"];
        DropDownList4.DataTextField = "CategoryName";
        DropDownList4.Items.Insert(0, "我会啦!HOHO");
        //下面这个方法也可以实现
        //DropDownList4.Items.Insert(0,new ListItem("0", "111"));
        DropDownList4.SelectedIndex = 0;
        DropDownList4.DataBind();
    }