DropDownList SelectedIndexChanged不触发（AutoPostBack =“ true”）

Question

I have a dropdownList on my webpage inside update panel. When I select a different value from the drop-down list, nothing happens which means that the "SelectedIndexChanged" event is not firing.

ASPX Code:

<asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
    <ContentTemplate>
     <table class="table table-mv-vouchers" style="margin:0px;" cellspacing="0" cellpadding="0">
                        <caption class="mv-clearfix">                            
                         <asp:DropDownList ID="ddlShort" Width="150"  runat="server" AutoPostBack="True" ViewStateMode="Enabled"  EnableViewState="true"  OnSelectedIndexChanged="ddlShort_SelectedIndexChanged">
                            <asp:ListItem Text="By Estimate" Value="EstimateValue"></asp:ListItem>
                            <asp:ListItem Text="By Merchant" Value="MerchantName" Selected="True"></asp:ListItem>
                            <asp:ListItem Text="By Type" Value="MerchantCategory"></asp:ListItem>
                            <asp:ListItem Text="By Validity" Value="Validity"></asp:ListItem>                        
                        </asp:DropDownList>                                                          
                        </caption>
                        </table>
</ContentTemplate></asp:UpdatePanel>

Server Side Code:

protected void ddlShort_SelectedIndexChanged(object sender, EventArgs e)
{
    string ByShort = ddlShort.SelectedValue;
    if (ByShort != null)
    {
        DataSet dsAllMerchant = Main.Instance.serClient.GetMerchantList(null,true, ByShort, null,currentBaID,true);
        DataTable newdata = this.GenerateData(dsAllMerchant.Tables[0]);
        lvGiftVoucher.DataSource = newdata;
        lvGiftVoucher.DataBind();
    }
}

Answer 1

My problem was <caption class="mv-clearfix"> </caption> tag, I think this tag is not recognize. After deleting this tag dropdownlist is firing. Thanks all for your answering.

Answer 2

I think you should add a trigger to your UpdatePanel, like that:

<asp:updatepanel ...>
   <triggers>
       <asp:asyncpostbacktrigger controlid="DrpEmployeeType" eventname="SelectedIndexChanged" />
   </triggers>
</asp:updatepanel>

Answer 3

将UpdatePanel更新模式更改为始终

UpdateMode="Always"

Answer 4

Ensure that you have:

• a ScriptManager on your page
• an UpdatePanel which wraps the lvGiftVoucher markup
• provided a unique Id to you update-panel
• an AsyncPostbackTrigger for dropdown SelectedIndexChanged event
• set UpdateMode to Conditional
• AutoPostback = "True" for the dropdwonlist (you already did it)

Dropdown markup (as is, just remove the updatepanel wrap)

<table class="table table-mv-vouchers" style="margin:0px;" cellspacing="0" cellpadding="0">
<caption class="mv-clearfix">                            
 <asp:DropDownList ID="ddlShort" Width="150"  runat="server" AutoPostBack="True" ViewStateMode="Enabled"  EnableViewState="true"  OnSelectedIndexChanged="ddlShort_SelectedIndexChanged">
    <asp:ListItem Text="By Estimate" Value="EstimateValue"></asp:ListItem>
    <asp:ListItem Text="By Merchant" Value="MerchantName" Selected="True"></asp:ListItem>
    <asp:ListItem Text="By Type" Value="MerchantCategory"></asp:ListItem>
    <asp:ListItem Text="By Validity" Value="Validity"></asp:ListItem>                        
</asp:DropDownList>                                                          
</caption>
</table>

UpdatePanel mark-up

<asp:UpdatePanel runat="server" id="up1" UpdateMode="Conditional" ChildrenAsTrigger="False">
    <Triggers>
        <asp:AsyncPostbackTrigger ControlId="ddlShort" EventName="SelectedIndexChanged" />
    </Triggers>
    <ContentTemplate>
        <!-- lvGiftVoucher markup here -->
    </ContentTemplate>
</asp:UpdatePanel>

Answer 5

我同意Sachu .....服务器端编码，在“ PageLoad事件”上..（！IsPostback）事件应在内部发生并调用“ Drop downList”

Answer 6

is your webpage created with master page? If so then check that your form tag is in which page master page/webpage. If it is in master page then simple emit that one and use form tag in webpage.

Answer 7

The same code is working fine in my PC....

Edited,

try this

add following code inside your Update panel

<Triggers>
    <asp:PostBackTrigger ControlID="ddlshort" />
    <asp:AsyncPostBackTrigger ControlID="ddlshort" EventName="SelectedIndexChanged"  />
</Triggers>

hope this work....

Answer 8

try the following:
1. add a try-catch block and see if you are getting any exception.
2. if your update panel UpdateMode is conditional , then you have to manually call Update() method or the panel will not update.