Upload file ASP.NET 5

I'm trying to upload a file in ASP.NET 5 but the two ways I've seen on internet fail. With XMLHttpRequest here is my server side code:

 public async Task<ActionResult> UploadSWF()
 {
     StreamReader reader = new StreamReader(Request.Body);
     var text = await reader.ReadToEndAsync();
     return View();
 }

[EDIT 1]: And my client side:

var client = new XMLHttpRequest();
function upload() 
{
   var file = document.getElementById("uploadfile");
   var formData = new FormData();
   formData.append("upload", file.files[0]);
   client.open("post", "/Home/UploadSWF", true);
   //client.setRequestHeader("Content-Type", "multipart/form-data");
   client.setRequestHeader("Content-Type", "application/x-shockwave-flash");
   client.send(formData);
}

But the only thing I can get from this is:

------WebKitFormBoundaryX1h5stVbtaNe6nFw Content-Disposition: form-data; name="upload"; filename="data.swf" Content-Type: application/x-shockwave-flash CWS ;"

[EDIT 2]:Here is the code how I get this:

 public ActionResult UploadSWF()
    {
        Stream bodyStream = Context.Request.Body;
        var sr = new StreamReader(bodyStream);
        var test = sr.ReadToEnd();
        return View();
    }

So I get the name of the file and the content-type but not its content.

This answer https://stackoverflow.com/a/26445416/1203116 is copying the stream into a file however the file creation part isn't working for me, I don't know what's going on but nothing happens. So I tried to do the same with a MemoryStream and I got an empty string.

So finally I tried another way, using IFormFile like shown here: https://github.com/aspnet/Mvc/blob/437eb93bdec0d9238d672711ebd7bd3097b6537d/test/WebSites/ModelBindingWebSite/Controllers/FileUploadController.cs This interface should be in Microsoft.AspNet.Http which I've added to my project but I'm still not able to access it. I can't see any IFormFile in this namespace.

[EDIT 1]: The first method I've tried is by using HttpPostedFileBase like I was used to in ASP.NET MVC 5 but it was not working in my vNext project. I always got an MissingMethodException. My code on client side was:

<form action="/home/UploadSWF" method="POST" enctype="multipart/form-data">
        <input type="file" name="file" accept=".swf, application/x-shockwave-flash/*">
        <input type="submit" name="submit" />
    </form>

And in my controller:

public ActionResult UploadSWF(HttpPostedFileBase file)
{
     return View();
}