选择索引上的组合框仅在按下输入时才会触发

Question

Hello，因为标题声明我的OnSelectedIndexChanged事件仅在您选择项目时触发，然后按 Enter 。我的组合框和gridview从数据源中获取它们的值。 OnSelectedIndexChanged gridview过滤器，但组合框始终具有所有值。有没有想过为什么会这样？

ASP

<asp:combobox ID="cbCustomer" runat="server" AutoCompleteMode="SuggestAppend" AutoPostBack="True" 
    DataSourceID="dataSourceCBCust" DataTextField="CUST_NAME" DataValueField="CUST_NAME" MaxLength="0" 
    style="display: inline;" OnSelectedIndexChanged="cbCustomer_SelectedIndexChanged">
</asp:combobox>
<asp:UpdatePanel ID="upCustomer" runat="server" ChildrenAsTriggers="true" UpdateMode="Conditional">
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="cbCustomer" EventName ="SelectedIndexChanged" />   
    </Triggers>
       <ContentTemplate>
            <asp:GridView ID="gvCustomer" runat="server" AllowPaging="True" DataSourceID="dataSourceGVCust" 
                 AutoGenerateColumns="True" Visible="true" ShowHeaderWhenEmpty="True">  
           </asp:GridView>  
       </ContentTemplate> 
</asp:UpdatePanel>

VB

Protected Sub cbCustomer_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbCustomer.SelectedIndexChanged
     'do stuff
End Sub