Download a file in an ajax request without running into a long querystring

Question

I have an asp.net MVC site and a controller action that looks like this:

  public ActionResult GeneratePPT(MyParams deckParams)
  {
      string template = Server.MapPath("/PPTTemplate.pptx");
      var results = _model.GeneratePPT(template);
      return File(results.Content, "application/vnd.ms-powerpoint", results.FileName);
  }

The issue is: MyParams object is getting very large (lots of parameters) so I would like to change this from a querystring to an ajax post to avoid long querystring issue (as I'm hitting the limit for Internet Explorer of 2083 characters in the URL.

the problem is that I don't see how I could return a file as part of a JsonResponse so I'm looking for recommendations on how I could both:

1. Get around the Internet Explorer 2083 character limit in URL
2. Have the ability to return a PowerPoint file

I had an idea of doing an ajax post to the server, having the server save a file and just return a path in a jsonResponse. Then have the client hit the server again to get the file. Does this make sense? Is there a more elegant way to do this in one step?

Answer 1

I would create normal form and controller Action that return's FileResult:

@model MyApplication.Models.MyParams 

@using (Html.BeginForm("GeneratePPT", "PttDownloader", FormMethod.Post, new { id = "downloadTestForm"}))
{
    //form data here 
    @Html.HiddenFor(model => Model.name)
    @Html.HiddenFor(model => Model.age)

     <input type="submit"/>
}

Action of normal controller:

using System;
using System.Web.Mvc;
using System.Net.Mime;

namespace MyApplication.Controllers
{
    public class PttDownloaderController : Controller
    {
        public FileResult GeneratePPT(MyParams deckParams)
        {
            try
            {
                //do something with deckParams...
                //deckParams.name
                //deckParams.age
                string template = Server.MapPath("/PPTTemplate.pptx");
                var results = _model.GeneratePPT(template);// provide _model

                return File(results.Content, MediaTypeNames.Application.Octet, results.FileName);
            }
            catch (Exception)
            {
                return null;
            }       
        }
    }
}

Form can be submitted by typical <input type="submit" /> or if you need to invoke this from Javascript you can use example below, both ways will always return file for download:

var download = function() {     

    var downloadTestForm = $('#downloadTestForm');
    downloadTestForm.submit();
};