UploadControl - How to upload a file via AJAX

This example is a standalone illustration of the File Upload - AJAX Uploading demo. It illustrates how to upload a file via the MVC UploadControl Extension.

- Specify the UploadControl settings: define the Name property and the CallbackRouteValues.Action method that should handle the file uploading;
- Wrap the UploadControl definition/PartialView within a form in order to post the selected file into the server memory;
- Introduce any custom trigger that should upload a file on demand, for example, the MVC Button Extension;
- Handle the client-side Button Click event. Call the client-side Upload method to post the selected file into the server memory;
- Handle the CallbackRouteValues.Action method. Retrieve the posted file via the UploadControlExtension.GetUploadedFiles method. Specify the uploading ValidationSettings and the "UploadComplete" handler as parameters;
- Handle the "UploadComplete" handler and save the posted file.

If it is necessary to pass any information to the client:
- Use the "UploadComplete" event handler's e.CallbackData property (take special note of the character case);
- Retrieve the passed information in the client-side FileUploadComplete event handler via the e.callbackData property (take special note of the character case).