How to Update an UpdatePanel after AjaxFileUpload UploadCompleteAll (ASP.NET)

The AjaxFileUpload control that's part of the AJAX Control Toolkit, works great for easily uploading multiple files at once.  However, it gets a little tricky if you want to update an UpdatePanel after all the files have finished uploading, especially if the UpdatePanel contains a GridView.  

Because the upload functionality of the AjaxFileUpload control happens in a hidden frame posted to the same url as the current page, and not by using the full postback of an UpdatePanel, it can never refresh the UpdatePanel using the code behind OnUploadCompleteAll.  Instead you need to refresh the UpdatePanel using OnClientUploadCompleteAll.  In order to do this we use the following: OnClientUploadCompleteAll="AjaxFileUpload1_ClientUploadCompleteAll" and refresh the UpdatePanel using __doPostBack javascript like this:

<script type="text/javascript">        function AjaxFileUpload1_ClientUploadCompleteAll(sender, args) {            __doPostBack('<%= PhotosGridUpdatePanel.ClientID %>', '');        }    </script>

<asp:Image id="MyThrobberImage" runat="server" ImageUrl="~/admin/css/images/uploading.gif" style="display:none" />        <ajaxToolkit:AjaxFileUpload ID="AjaxFileUpload1" runat="server" Padding-Bottom="4"            Padding-Left="2" Padding-Right="1" Padding-Top="4" ThrobberID="MyThrobberImage"             OnUploadComplete="AjaxFileUpload1_OnUploadComplete" OnClientUploadCompleteAll="AjaxFileUpload1_ClientUploadCompleteAll"             MaximumNumberOfFiles="10"            AllowedFileTypes="gif,png,jpg,jpeg"  />

 Then we need to add OnPreRender="PhotosGridUpdatePanel_PreRender" to the UpdatePanel. (Note you could also use: OnLoad):

<asp:UpdatePanel id="PhotosGridUpdatePanel" runat="server"  OnPreRender="PhotosGridUpdatePanel_PreRender">                          <ContentTemplate>                                     <asp:GridView ID="PhotosGridView" runat="server" AllowPaging="True" AllowSorting="True"                                      DataKeyNames="PhotoId" DataSourceID="ObjectDataSource1"  PageSize="10">                                <Columns>                                 <asp:BoundField DataField="PhotoId" HeaderText="Id" SortExpression="PhotoId" Visible="False" /></Columns>                                <EmptyDataTemplate>                                    <p>No photos added yet.</p>                                </EmptyDataTemplate>                             </asp:GridView></ContentTemplate></asp:UpdatePanel>

Then in your code behind file add the protected void PhotosGridUpdatePanel_PreRender(object sender, EventArgs e)function:

    protected void PhotosGridUpdatePanel_PreRender(object sender, EventArgs e)    {            if (Request.Form["__EVENTTARGET"] != null && Request.Form["__EVENTTARGET"] != string.Empty)            {                // This code will only be executed if the partial postback                //  was raised by a __doPostBack('UpdatePanel1', '')                if (Request.Form["__EVENTTARGET"] == PhotosGridUpdatePanel.ClientID)                {                    // Use this to Update the GridView after AjaxFileUpload1                    PhotosGridView.DataBind();                }            }    }

By using if (Request.Form["__EVENTTARGET"] == PhotosGridUpdatePanel.ClientID), we will only refresh the PhotosGridView when the javascript __doPostBack is raised. 

So essentially, the GridView inside the UpdatePanel will work correctly when an item from the GridView is Edited/Updated or Deleted. 

Note, this should work with the September 2013 AjaxControlToolkit .NET 4.5 both on localhost and on a web server. 

However, the July 2013 AjaxControlToolkit .NET 4.5 worked fine on my localhost, but on my web server, I would get the following error when trying to Edit or Delete items from the GridView:

Could not load control AjaxControlToolkit.AjaxFileUpload. The script reference(s) of this control was not loaded correctly. If AjaxControlToolkit.config is used, probably this control is not registered properly.

To understand all this a little better, see Easily refresh an UpdatePanel, using JavaScript and Are you making these 3 common ASP.NET AJAX mistakes?