第一件事，第一，不绑定在订单实体。千万不要绑定到EF对象，总是试图用的视图模型。使得视野中的生活比较简单，那就是这里的目标。

First thing's first, don't bind to the Order entity. Never bind to an EF object, always try and use a ViewModel. Makes life simpler for the View, and that is the goal here.

所以，有这样的视图模型：

So, have a ViewModel like this:

public class CreateOrderViewModel
{
   public int OrderId { get; set; }
   public DateTime OrderDate { get; set; }
   public int SelectedProductId { get; set; }
   public IEnumerable<SelectListItem> Products { get; set; }
}

这就是它现在。

返回，为您的查看你的 [HTTPGET] 控制器动作：

Return that to your View in your [HttpGet] controller action:

[HttpGet]
public ActionResult Create()
{
   var model = new CreateOrderViewModel
   {
      Products = db.Products
                   .ToList() // this will fire a query, basically SELECT * FROM Products
                   .Select(x => new SelectListItem
                    {
                       Text = x.ProductName,
                       Value = x.ProductId
                    });
   };

   return View(model);
}

然后呈现出产品的名单：（基本的HTML除外）

Then to render out the list of Products: (basic HTML excluded)

@model WebApplication.Models.CreateOrderViewModel

@Html.DropDownListFor(model => model.SelectedProductId, Model.Products)

我不知道该怎么做的唯一事情就是绑定到DateTime字段。我猜你会需要它呈现出的日期选择器什么的一个扩展方法（HTML帮助）。该视图（创建新订单），就默认为 DateTime.Now 。

现在，到 [HttpPost] 控制器动作：

[HttpPost]
public ActionResult Create(CreateOrderViewModel model)
{
   try
   {
      // TODO: this manual stitching should be replaced with AutoMapper
      var newOrder = new Order
      {
         OrderDate = DateTime.Now,
         OrderProduct = new OrderProduct
         {
            ProductId = SelectedProductId
         }
      };

      db.Orders.AddObject(newOrder);
      return RedirectToAction("Index");
   }
   catch
   {
      return View();
   }
}

现在，我也觉得你的EF模型需要的工作。

Now, i also think your EF model needs work.

要我（英文术语），一个产品可以有多个订单，一个订单可以有很多产品。​​

因此​​，它应该是一个多对许多。目前，它是一个1-1冗余连接表。你有没有产生来自DB？如果是这样，你可能DB需要的工作。

So, it should be a many-to-many. Currently it's a 1-1 with a redundant join table. Did you generate that from a DB? If so, your DB possibly needs work.

您应该有一个导航属性​​时调用的产品的订单实体，它引用的产品的集合，通过无声成为可能加盟在连接表许多一对多。

You should have a navigational property called Products on the Order entity, which references a collection of Product, made possible by a silent join to the join table in the many-to-many.

这也意味着你不再有一个DropDownList，而是一个MultiSelectDropDownList。

This also means you no longer have a DropDownList, but a MultiSelectDropDownList.