@inject HttpClient HttpClient

<TelerikUpload OnRemove="@OnUploadRemove" RemoveUrl="@RemoveUrl" />

@code {
    private string RemoveUrl { get; set; } = "api/upload/remove";

    private async Task OnUploadRemove(UploadEventArgs args)
    {
        // code for non-initial files
        // send optional custom data to the controller
        args.RequestData.Add("requestKey", "custom value");

        // code for initial files
        // call the RemoveUrl
        if (args.Files.First().Status == UploadFileStatus.Blank)
        {
            var multipartContent = new MultipartFormDataContent();

            multipartContent.Add(new StringContent(args.Files.First().Name), "files"); // "files" must match the RemoveField value
            multipartContent.Add(new StringContent("requestKey"), "custom value"); // send optional custom data to the controller

            await HttpClient.PostAsync(RemoveUrl, multipartContent);
        }
    }
}

builder.Services.AddHttpClient();