问如何使用MVC5获取输入文件字段的值？

EN

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

public ActionResult Upload(HttpPostedFileBase file, FormCollection form)
{
    if (Request.QueryString["oauth_verifier"] != null && Session["RequestToken"] != null)
    {
        // Flickr relevant code...
        var tmpFilePath = Server.MapPath("~/App_Data/Uploads/Pictures");

        if (file == null || file.ContentLength == 0)
        {
            return RedirectToAction("Index"); // It keeps hitting this!
        }

        var filename = Path.GetFileName(file.FileName);
        var path = Path.Combine(tmpFilePath, filename);

        if (System.IO.File.Exists(path))
        {
            System.IO.File.Delete(path);
        }

        file.SaveAs(path);

        string photoId = flickr.UploadPicture(path, "Test picture");

        if (String.IsNullOrEmpty(photoId))
        {
            System.Diagnostics.Debug.WriteLine("Upload failed!");
        }

        System.IO.File.Delete(path);
    }
    else
    {
        // Flickr relevant code...
    }

    return View("Test");
}