public class UploadFileInfo

<DxUpload Name="myFile" UploadUrl="https://localhost:10000/api/Upload/Upload/" 
          FileUploadStarted="@OnFileUploadStarted">
</DxUpload>
<div class="alert alert-info @(MessageVisible? " visible" : " invisible")">@MyMessage</div>

@code {
    void OnFileUploadStarted(FileUploadEventArgs e) {
        MyMessage = "Upload of the " + e.FileInfo.Name + " file was started.";
        MessageVisible = true;
        InvokeAsync(StateHasChanged);
    }
}