How to post an array of files in ASP.NET MVC 3?

If you want to upload not only one file, you need to use enctype="multipart/form-data" in your form.

@using (Html.BeginForm("", "Client", FormMethod.Post, new {enctype="multipart/form-data"}))

And controller:

[HttpPost]
public ActionResult AddPart(IEnumerable<HttpPostedFileBase> files) 

All other parts is ok.