<style>
    .k-upload-status .k-upload-action:nth-of-type(2n+1) {
        display: none;
    }
</style>

@inject NavigationManager NavigationManager

<TelerikUpload SaveUrl="@SaveUrl"
               RemoveUrl="@RemoveUrl"
               OnUpload="@OnUploadHandler">
</TelerikUpload>

@code {
    async Task OnUploadHandler(UploadEventArgs e)
    {
        // a flag to make uploads error out, see the controller
        e.RequestData.Add("shouldFail", "true"); 
    }

    // a sample way of generating the URLs to the endpoint
    public string SaveUrl => ToAbsoluteUrl("api/upload/save");
    public string RemoveUrl => ToAbsoluteUrl("api/upload/remove");

    public string ToAbsoluteUrl(string url)
    {
        return $"{NavigationManager.BaseUri}{url}";
    }
}

        [HttpPost]
        public async Task<IActionResult> Save(IEnumerable<IFormFile> files)
        {
            string shouldFail = Request.Form["shouldFail"]; // the key from the OnUpload event that will make the request fail
            if (shouldFail != null && shouldFail.ToLowerInvariant().Equals("true"))
            {
                Response.StatusCode = 401;
                return new EmptyResult();
            }