Upload File Validation using jQuery Forms in ASP.NET MVC

Question

Hi,

I am working on some ASP.NET MVC code which makes use of the jQuery Forms plug-in to allow users to upload files.

The Form:

<% using (Html.BeginForm("SaveAttachments", "Data", FormMethod.Post, new { enctype = "multipart/form-data", id="SaveAttachments" })) {%>   
        <input type="file" name="consentform" size=30/>
     <input type="file" name="infosheet" size=30/>     
     <input type="file" name="approval" size=30 />         
<%} %>

The form is submitted using jQuery with the Form plugin:

$('#SaveAttachments").ajaxSubmit({
                    success: function(html, status) {
                        $("#response").append(html);
                    }
});

It is handled by a controller action name SaveAttachments:

public ActionResult SaveAttachments(HttpPostedFileBase consentform, HttpPostedFileBase infosheet, HttpPostedFileBase approval)
        {
            string message = SaveFiles(consentform, infosheet, approval)
            return Content(message);
        }

This works well except in the case of errors which prevent the controller action from being called; Specifically when the file size is too large and a HttpException "Maximum Request Length is Exceeded" is thrown.

What I require is a way of updating the user with a suitable message when such errors occur.

I have considered the following:

1. Try and use the Forms plugin to detect and handle this within the ajaxSubmit() - this doesn't appear possible.
2. Add some client side validation on the files to upload - without using Flash or ActiveX, I can't find a way of checking file size etc. in IE and FF.
3. Handle the HttpException thrown by the Controller.Execute() method, and communicate this with the SaveAttachments() action - I was considering overriding the controller.Execute() method to allow this.

What is the best method of achieving the necesary validation, and if there is no clean way is handling the exception an acceptable workaround?

Thanks.

Edit:

I have been reduced to two options:

1. Use Flash/ActiveX/Silverlight for more versatile file upload form.
2. Find a way to direct text from the content length exceeded exception handler to the displaying the status in the form. As the file upload form is submitted using an iFrame I'm not sure I can do this..

Answer 1

Can't you just use jQuery's ajaxError function? http://docs.jquery.com/Ajax/ajaxError#callback

Also, you may want to be more specific about which plugin you are using. ajaxSubmit() is not core jquery.