Server Events

Demo uploads land in a temporary store and are swept after 60 minutes. To keep files, handle FileUploaded — see Single File for the complete save pattern.
Server-Side FileUploaded Event

Handle the server-side FileUploaded event on the next Web Forms postback. Upload files first, then submit the page to process the uploaded GUIDs on the server.

Two things that trip people up: FileUploaded fires on the postback, not during the transfer — without a submit, your handler never runs and the temp copy is swept after 60 minutes. If your page has no submit flow of its own, set AutoPostBack="true" on the control and the page posts back automatically when the batch finishes, exactly like v4 did. And the destination you pass to CopyFile/MoveTo accepts ~/ app-relative paths (resolved against the site root) or absolute paths; a bare relative path is also anchored at the site root, never the worker process directory.
Drag & drop files here, or paste from clipboard
Processed Files
<%-- ASPX Markup --%>
<au:AjaxFileUpload ID="Uploader1" runat="server"
 OnFileUploaded="Uploader1_FileUploaded"
 ShowProgress="true" />

<%-- No submit flow on the page? Post back automatically when the
     batch finishes (v4 behaviour) instead of adding a button: --%>
<au:AjaxFileUpload ID="Uploader2" runat="server"
 AutoPostBack="true"
 OnFileUploaded="Uploader1_FileUploaded" />

<asp:Button runat="server" Text="Process Uploaded Files"
 OnClick="BtnProcess_Click" />

// Code-behind or <script runat="server">
protected void Uploader1_FileUploaded(object sender, FileUploadedEventArgs e)
{
 var uploadService = new UploadService();
 var targetFolder = Server.MapPath("~/App_Data/Processed");
 var safeFileName = Path.GetFileName(e.FileName ?? string.Empty);
 Directory.CreateDirectory(targetFolder);
 var savedFileName = Guid.NewGuid().ToString("N")
  + Path.GetExtension(safeFileName);
 uploadService.CopyFile(
 e.FileGuid,
 Path.Combine(targetFolder, savedFileName));
}
Try It

Upload one or more files, then click Process Uploaded Files to raise FileUploaded during the page postback.