ASP.NET-MVC中Form Form上的FormCollection为空

[HttpPost]
public ActionResult MyAction(FormCollection formCollection)
{
    // Your code here
}

@using (Html.BeginForm("MyAction", "MyController", FormMethod.Post))
{
    @Html.TextBox("MyField")
   <input type="submit" value="Submit" />
}

@using (Html.BeginForm("MyAction", "MyController", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
   <input type="file" name="myFile" />
   <input type="submit" value="Submit" />
}

[HttpPost]
public ActionResult MyAction(HttpPostedFileBase myFile, FormCollection formCollection)
{
    // Your code here
}