ASP.NET MVC3页面传值问题

页面表单代码如下：
@using (Html.BeginForm("OrderReady", "UserManager", FormMethod.Post, new { id = "order" }))
{

<span>尺码:</span>
<select id="Size">
<option>38</option>
<option>39</option>
<option>40</option>
<option>41</option>
<option>42</option>
<option>43</option>
</select><br />
<span>我要买：</span>
<input type="text" id="Quantity" name="Quantity" value="1" style="width: 30px; text-align: center;" />
@Html.Hidden("Hno", @item.Hno);
<span>件</span>
<br />
<input type="image" src="../../Content/Photos/buy1.jpg"/>
}

然而跳转到
public ActionResult OrderReady(order order)
{
order.Sno = HttpContext.User.Identity.Name;

return Content("用户名:"+order.Sno+" 鞋编号:"+order.Hno+" 尺码:"+order.Size+" 数量："+order.Number);
}
的方法中，鞋的尺码和数量的值都没有传过来，求解！