Completed
Last Updated: 22 Apr 2026 08:13 by ADMIN
Release 2025 Q3 (Aug)
Stefan
Created on: 03 Jun 2025 15:22
Category: Upload
Type: Bug Report
8
Uploaded file data not available in the OnSuccess event

Description

File data is not available in the Upload's OnSuccess event.

Regression in version 9.0.0 introduced with the addition of the chunk upload functionality.

https://github.com/telerik/blazor/blob/master/js/telerik-blazor/src/upload/upload.ts#L282-L288

Steps To Reproduce

  1. Attach a handler to the OnSuccess event:
<TelerikUpload SaveUrl="/api/upload/save"
               RemoveUrl="/api/upload/remove"
               OnSuccess="@OnSuccessHandler" />

@code {
    async Task OnSuccessHandler(UploadSuccessEventArgs e)
    {
        foreach (var file in e.Files)
        {
            Console.WriteLine($"Name = {file.Name}, Size = {file.Size}, Extension = {file.Extension}");
        }

        StateHasChanged();
    }
}
  1. Upload a file and try to access its Name, Size, and Extension properties in the event handler.

Actual Behavior

The properties have their default values (null for Name and Extension and 0 for Size).

Expected Behavior

The actual file data is accessible in the OnSuccess event handler.

Browser

All

Last working version of Telerik UI for Blazor (if regression)

8.1.1

5 comments
ADMIN
Ivan Danchev
Posted on: 22 Apr 2026 08:13

Hello,

Thank you for clarifying the issue.

Its fix is included in version 13.2.0: https://www.telerik.com/support/whats-new/blazor-ui/release-history/telerik-ui-for-blazor-13-2-0  (the "Request data is missing on chunk upload success" entry under Upload).

Regards,
Ivan Danchev
Progress Telerik

Love the Telerik and Kendo UI products and believe more people should try them? Invite a fellow developer to become a Progress customer and each of you can get a $50 Amazon gift voucher.

Jonathan
Posted on: 20 Apr 2026 21:07
Thanks for the response, Ivan, the above issue does seem to be fixed.

I was linked here by a different issue which still exists in v12 and v13: When using chunked upload the success response body is always empty in UI for Blazor | Telerik Forums .
ADMIN
Ivan Danchev
Posted on: 09 Apr 2026 14:18

Hello,

I've tested the Upload in version 12.2.0 and all the file data is available in the OnSuccess event. A sample project is attached. See the screenshot below taken using the attached project. The file.Name, file.Size, and file.Extension values are successfully accessed in the OnSuccess event handler and are displayed on the page: 

 

Regards,
Ivan Danchev
Progress Telerik

Love the Telerik and Kendo UI products and believe more people should try them? Invite a fellow developer to become a Progress customer and each of you can get a $50 Amazon gift voucher.

Attached Files:
Jonathan
Posted on: 02 Apr 2026 16:45
I'm having this exact issue in v.12.2.0. Is there a workaround?
ADMIN
Ivan Danchev
Posted on: 27 Jun 2025 11:01

Hello,

The issue has been fixed in version 9.1.0, released on June 27, 2025: https://www.telerik.com/support/whats-new/blazor-ui/release-history/telerik-ui-for-blazor-9-1-0

Regards,
Ivan Danchev
Progress Telerik

Love the Telerik and Kendo UI products and believe more people should try them? Invite a fellow developer to become a Progress customer and each of you can get a $50 Amazon gift voucher.