asp.net 急求方法源码

制作一组联动的“学年-学期-分院-教师”的下拉列表。当最后选择教师后自动生成一个表格，这个怎么触发最后一个 DropDownList控件让table自动生成呢。

教师1
教师2
教师3

function test(){
alert(444);
}

直接用onchange事件吧，这样在不更改教师的情况下减少了重新刷新table造成的性能消耗

Aspx页面：

<asp:DropDownList ID="ddlClass" runat="server" OnSelectedIndexChanged="ddlClass_SelectedIndexChanged" />
<asp:DropDownList ID="ddlTeacher" runat="server" OnSelectedIndexChanged="ddlTeacher_SelectedIndexChanged" />

后台Cs：
public string[] arrayClass = { "Class1", "Class2", "Class3" };
public string[] arrayTeachers1 = { "T1", "T2", "T3" };
public string[] arrayTeachers2 = { "T4", "T5", "T6" };
public string[] arrayTeachers3 = { "T7", "T8", "T9" };

        protected void Page_Load(object sender, EventArgs e)
        {
            if(!IsPostBack)
            {
                ddlClass.DataSource = arrayClass;
                ddlClass.DataBind();
                ddlClass.SelectedIndex = 0;

                ddlTeacher.DataSource = arrayTeachers1;
                ddlTeacher.DataBind();
            }
        }

        protected void ddlClass_SelectedIndexChanged(object sender, EventArgs e)
        {
            switch(ddlClass.SelectedIndex)
            {
                case 0:
                    ddlTeacher.DataSource = arrayTeachers1;
                    break;
                case 1:
                    ddlTeacher.DataSource = arrayTeachers2;
                    break;
                case 2:
                    ddlTeacher.DataSource = arrayTeachers3;
                    break;
            }

            ddlTeacher.DataBind();
        }

        protected void ddlTeacher_SelectedIndexChanged(object sender, EventArgs e)
        {
            if(ddlTeacher.SelectedValue.Equals("T1"))
            {
                //生成Table
            }
        }
    }