关联框的问题【附代码】

Question

实现代码基本如下，但就是没效果，我选择第一个框后，第二个框并没有变化
.NET代码：                                学院：           
                                <asp:DropDownList ID="college" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged"
                                    Width="221px" Enabled="False">
                                </asp:DropDownList>CS代码： protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["strcon"]);
        con.Open();
        string college1 = this.college.Text;
        SqlDataAdapter sda = new SqlDataAdapter(" select speciality from ts_unit_collgeSpeciality where collegeName ='" + college1 + "'", con);
        DataSet ds = new DataSet();
        sda.Fill(ds, "ts_unit_collgeSpeciality");
        //DataRowView rowview = ds.Tables["ts_xs_professionalCourses"].DefaultView[0];
        this.speciality.DataSource = ds.Tables["ts_unit_collgeSpeciality"];        this.speciality.DataTextField = "speciality";
        this.speciality.DataBind();
        con.Close();
    }

Answer 1

string college1 = this.college.Text;//断点跟踪看这个值是否正确
最好用先指定Value值，然后用SelectedValue 获得