Question

我有以下代码。

我想要的是当ddlProvince下拉列表被更改时，抛出事件SelectedIndexChanged，但是永远不会访问该方法。

<asp:UpdatePanel ID="pnlCountries" runat="server">
<Triggers>
    <asp:AsyncPostBackTrigger ControlID="ddlProvince" EventName="SelectedIndexChanged" />
</Triggers>
<ContentTemplate>
<tr>
    <td><asp:Literal ID="Literal37" Text="<%$Resources:glossary,country %>" runat="server"/></td>
    <td>

<asp:DropDownList ID="ddlCountries" CssClass="textbox" runat="server">
</asp:DropDownList>
<br />
<cc1:cascadingdropdown ID="cddCountries" runat="server" Category="Country" Enabled="True" LoadingText="<%$Resources:Glossary,loading %>" PromptText="<%$Resources:Glossary,country_choose %>" 
ServiceMethod="GetCountries" TargetControlID="ddlCountries">
</cc1:cascadingdropdown>
<asp:RequiredFieldValidator CssClass="errortext" Text="<%$Resources:Glossary,required %>" SetFocusOnError="true" ID="rfvcboScenario" runat="server" InitialValue="" ControlToValidate="ddlCountries" Display="Dynamic" />


    </td>
</tr>
<tr>
    <td><strong><asp:Literal ID="Literal9" Text="<%$Resources:Glossary,province %>" runat="server" /> *</strong></td>
    <td>
        <asp:DropDownList ID="ddlProvince" CssClass="textbox" runat="server">
        </asp:DropDownList>       
        <asp:RequiredFieldValidator CssClass="errortext" Text="<%$Resources:Glossary,required %>" SetFocusOnError="true" ID="RequiredFieldValidator1" runat="server" InitialValue="" ControlToValidate="ddlProvince" Display="Dynamic" />
    <cc1:CascadingDropDown ID="cddProvince" runat="server" TargetControlID="ddlProvince" ParentControlID="ddlCountries"   
        Category="Province" LoadingText="<%$Resources:Glossary,loading %>" prompttext="<%$Resources:Glossary,province_select %>" ServiceMethod="GetProvincesForCountry" >
    </cc1:CascadingDropDown>


</td>
</tr>
</ContentTemplate>
</asp:UpdatePanel>

目前此代码行永远不会被命中：

Protected Sub ddlProvince_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ddlProvince.SelectedIndexChanged
    ReportError("ddlProvince_SelectedIndexChanged", "")
End Sub

更新：之前我在ddlProvince控件上有了Autopostback =“true”属性，但这导致了一个完整的回发（问题也在这里描述：Drop Down List (in Update Panel) causing FULL PostBack!）

我错过了什么？

Answer 1

修改您需要为下拉列表设置AutoPostBack="true"。改变这个：

<asp:DropDownList ID="ddlProvince" CssClass="textbox" runat="server"> </asp:DropDownList>

到此：

<asp:DropDownList ID="ddlProvince" CssClass="textbox" runat="server" AutoPostBack="true" > </asp:DropDownList>

Answer 2

可能您没有在标记中设置OnSelectedIndexChanged事件，如上所示。

您应该设置三个属性：OnSelectedIndexChanged，AutoPostback＆amp; EnableViewState

<asp:DropDownList ID="ddlProvince" runat="server" 
     AutoPostBack="true" EnableViewState="true"
     OnSelectedIndexChanged="ddlProvince_SelectedIndexChanged">                
</asp:DropDownList>

如果你绑定了page_Load事件中的下拉列表，请将其置于!IsPostback条件检查中：

protected void page_Load ( object sender, EventArgs e )
{
     if(!IsPostBack)
     {
            //DropDownList data bind and all...
      }
}

updatepanel asynpostbacktrigger不会抛出已定义的事件？

2 个答案: