アップロードしたファイルを保存する ref: http://qiita.com/nakaji/items/f19a957b3b214bc96982

HomeController

using System.Web;
using System.Web.Mvc;

namespace WebApplication4.Controllers
{
    public class HomeController : Controller
    {
        [HttpGet]
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult Index(HttpPostedFileWrapper uploadFile)
        {
            if (uploadFile != null && uploadFile.ContentLength != 0)
            {
                uploadFile.SaveAs(Server.MapPath("~/uploads/") + uploadFile.FileName);
            }

            return View();
        }
    }
}

index.cshtml

<h2>ファイルアップロードのサンプル</h2>

@using (Html.BeginForm("Index", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    <input type="file" name="uploadFile" />
    <input type="submit" />
}