ASP.NET - reload a dropdown?

I have a dropdown which shows filesnames and when the index is changed, the slected file is offered for download. I also have a button which creates new files ... now after a new file was created, the new filename should also be shown in the dropdown. It works fine, when I refresh the page, but this is not what I want.

I tried putting the dropdown in an updatepanel and giving it the file create button id, it failed ... is this the correct apporach or is there an easier way?

Thanks!

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I just cant get it to work, this is my code:

<asp:UpdatePanel ID="UP_ExportInvoices" runat="server" UpdateMode="Always">
     <ContentTemplate>
         <asp:DropDownList ID="DDL_ExportFileDownLoad" runat="server" AutoPostBack="true"
                        OnSelectedIndexChanged="DDL_ExportFileDownLoad_SelectedIndexChanged">
         </asp:DropDownList>
     </ContentTemplate>
</asp:UpdatePanel>

I was thinking that if the UpdateMode is set to Always, that the content is always updated? I also have that button (asp:ImageButton) which resides outisde this UpdatePanel. I tried adding a Trigger fpr that button, but开发者_运维问答 it did not work. What am I making wrong. So far, im only thrwoing exceptions or the dropdown is not updated.

Thanks :)

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If you are creating the file in the same page, then just append the file name to the dropdown. Can you do this trick in your application?

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Does you button posts back the page? If yes, then you need to rebind the drop-down again after you create the file in button click handler.

If button makes partial post-back (say it is placed within UpdatePanel) to the server then above will be still applicable but dropdown should also be in UpdatePanel.

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You need to ensure that the Button is a trigger for the Update Panel, or is a child within it.

Here is a full explanation:

http://www.asp.net/ajax/tutorials/understanding-asp-net-ajax-updatepanel-triggers

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You need to place the button within the UpdatePanel. This will cause a partial postback and the dropdown should re-bind, showing the new item. Alternatively you can include JavaScript in your page which adds the new item to the dropdown list on the client-side, however this can sometimes cause problems with ASP's automatic event validation.