使用Vb.Net根据Asp.Net中的另一个DropDownList值更改DropDownList

<asp:DropDownList ID="ddl1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddl1_SelectedIndexChanged">
    <asp:ListItem Text="Option 1" Value="1"></asp:ListItem>
    <asp:ListItem Text="Option 2" Value="2"></asp:ListItem>
    <asp:ListItem Text="Option 3" Value="3"></asp:ListItem>
</asp:DropDownList>

<asp:DropDownList ID="ddl2" runat="server">
    <!-- 根据ddl1的选择值动态添加选项 -->
</asp:DropDownList>

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    AddHandler ddl1.SelectedIndexChanged, AddressOf ddl1_SelectedIndexChanged
End Sub

Protected Sub ddl1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
    Dim selectedValue As String = ddl1.SelectedValue

    ddl2.Items.Clear()

    Select Case selectedValue
        Case "1"
            ddl2.Items.Add(New ListItem("Option 1-1", "1-1"))
            ddl2.Items.Add(New ListItem("Option 1-2", "1-2"))
            ddl2.Items.Add(New ListItem("Option 1-3", "1-3"))
        Case "2"
            ddl2.Items.Add(New ListItem("Option 2-1", "2-1"))
            ddl2.Items.Add(New ListItem("Option 2-2", "2-2"))
            ddl2.Items.Add(New ListItem("Option 2-3", "2-3"))
        Case "3"
            ddl2.Items.Add(New ListItem("Option 3-1", "3-1"))
            ddl2.Items.Add(New ListItem("Option 3-2", "3-2"))
            ddl2.Items.Add(New ListItem("Option 3-3", "3-3"))
    End Select
End Sub