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Ensuring OnFileUploaded Event Fires Automatically in RadAsyncUpload

Updated on May 28, 2026

Environment

Product	AsyncUpload for UI for ASP.NET AJAX
Version	all

The server-side OnFileUploaded event of the RadAsyncUpload component fires only during a postback. If you want this event to trigger automatically once a file is uploaded — without requiring additional actions like a button click — you need to initiate the postback programmatically using the client-side OnClientFilesUploaded event.

Incorrect or incomplete AJAX settings, as well as certain configurations in Page_Load, can also prevent this event from firing as expected.

This knowledge base article also answers the following questions:

How can I trigger the OnFileUploaded event without a button click?
Why does the OnFileUploaded event not fire in RadAsyncUpload after a file upload?
How do I configure RadAsyncUpload to refresh a grid after file upload?

Solution

Step 1: Correct Unsupported Configurations

Ensure that your RadAsyncUpload configuration is valid:

Remove conflicts between MultipleFileSelection and MaxFileInputsCount:
- Use MultipleFileSelection="Automatic" and omit MaxFileInputsCount, or
- Use MaxFileInputsCount and set MultipleFileSelection to "Single" or "Disabled".

Step 2: Trigger Postback from `OnClientFilesUploaded`

To trigger the postback programmatically after all files finish uploading:

Add the OnClientFilesUploaded event to your RadAsyncUpload component.
Use the __doPostBack method to initiate the postback from the client-side.

html

<telerik:RadAsyncUpload runat="server" ID="AsyncUpload1"
    RenderMode="Lightweight"
    MultipleFileSelection="Automatic"
    ChunkSize="1048576"
    HideFileInput="true"
    MaxFileSize="104857600"
    AllowedFileExtensions=".jpeg,.jpg,.png,.doc,.docx,.xls,.xlsx,.pdf,.xml,.eps,.pptx,.ppt"
    EnableAjax="true"
    TargetFolder="~/Files"
    OnClientFilesUploaded="OnClientFilesUploaded"
    OnFileUploaded="AsyncUpload1_FileUploaded" />

<script>
function OnClientFilesUploaded(sender, args) {
    __doPostBack(sender.get_uniqueID(), "");
}
</script>

Step 3: Add AJAX Settings in `Page_Load`

Ensure that the AJAX settings are added on every request in your Page_Load handler. This ensures that the postback triggered via __doPostBack is handled correctly as a partial update.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Try
        EnsureUploadFoldersExist()
    Catch ex As Exception
        PLog.Log(IDBType.IDBLog.ErrorLog, If(Session.SessionID, "NoSession"), _
                 "Upload folder creation error", ex.Message & " - " & ex.StackTrace)
    End Try

    ' Register AsyncUpload1 with RadAjaxManager
    Dim ajaxManager As RadAjaxManager = RadAjaxManager.GetCurrent(Page)
    If ajaxManager IsNot Nothing Then
        ajaxManager.AjaxSettings.AddAjaxSetting(AsyncUpload1, RGridAttachment)
        ajaxManager.AjaxSettings.AddAjaxSetting(AsyncUpload1, RGridClipboard)
    End If
End Sub

Step 4: Refresh the Grid in `OnFileUploaded`

In the server-side OnFileUploaded handler, rebind the grid to display the newly uploaded files.

Protected Sub AsyncUpload1_FileUploaded(sender As Object, e As FileUploadedEventArgs)
    ' RadAsyncUpload automatically saves e.File to TargetFolder.
    ' Just refresh the grid here to show the new file.
    RGridAttachment.Rebind()
End Sub

Additional Notes

Use OnClientFilesUploaded (plural) instead of OnClientFileUploaded to trigger a single postback after all files are uploaded.
Avoid manually saving the uploaded file inside OnFileUploaded if TargetFolder is already set, as the file is automatically moved there.
Correct markup errors such as duplicate attributes or unsupported configurations.