MVC，查看显示数据

Question

Hey, I am new to asp and I would like to ask you for some help. I built store with MvcMusicStore tutorial help. Now I want to add a View to manage orders which will display just OrderID (in Index View), then more info in Details View. Info will come from table which looks like this:

When I list OrderID, its multiplying because each product creates new record with the same OrderID in the table. Is there any way to display each Id just once?

Then I tried to display more info in Detaild View but I failed again. I used this code in Controller:

        public ActionResult Details(int id)
    {
        var orderdetail = storeDB.OrderDetails.Single(a => a.Order.OrderId == id);
        return View(orderdetail);
    }

but obviously it wont work because only one element can be displayed. I also tried with foreach loop in Details.aspx but I was getting some IEnumerables-related error. Any advice is welcome, sorry for newbie question and bad English. Thank you.

Edit: Here is Controller's code for Index View (Product in my table equals Album in tutorial):

        public ActionResult Index()
    {
        var manageorders = storeDB.OrderDetails
        .Include("Product").Include("Order")
        .ToList();
        return View(manageorders);
    }

And Details View code:

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/MasterPage.Master" Inherits="System.Web.Mvc.ViewPage<ss.Models.OrderDetail>" %>

Index

<div id="style3">manage orders</div>
<div id="style1">
<table>
    <tr>
        <th></th>
        <th>
        user
        </th>
        <th>
        data
        </th>
        <th>
        product
        </th>
        <th>
        quantity
        </th>

    </tr>

<% foreach (var item in Model) { %>

    <tr>
        <td>
            <%: Html.ActionLink("Edit", "Edit", new { id=item.Order.OrderId }) %> |
            <%: Html.ActionLink("Details", "Delete", new { id=item.Order.OrderId })%>
        </td>
        <td>
            <%: item.Order.Username %>
        </td>
                    <td>
            <%: item.Order.OrderDate %>
        </td>
        <td>
            <%: item.Quantity %>
        </td>
                    <td>
            <%: item.Quantity %>
        </td>
    </tr>

<% } %>

<p>
    <%: Html.ActionLink("Create New", "Create") %>
</p>

And error I am recieving:

Compiler Error Message: CS1579: foreach statement cannot operate on variables of type 'ss.Models.OrderDetail' because 'ss.Models.OrderDetail' does not contain a public definition for 'GetEnumerator'

Answer 1

Single() will throw an exception if there's more than 1 element in the sequence, so the error here is because each Order can have many OrderDetails (this is your IEnumerable-ish error). If you wanted to select the first match, when there could be many, use the First() method, which won't throw if there's more than one.

It depends really what your controller is working with - Orders or OrderDetails. This would be the difference between Orders/Details/1 and OrderDetails/Details/1 , where the first would be focussing on the whole order and all of its details, and the second would be looking at one specific line.

If you wanted to work with the order - which it looks like you're going for - then you'd need a reference of some kind from the Order to its collection of OrderDetails. If you're using something like Entity Framework like in the MusicStore tutorial, then you'll get this collection as part of your entity model. You would pass the Order to the view, and could then access the OrderDetails collection in a for each or similar loop eg

public ActionResult details(int id)
{
   Order viewModel = storeDb.Orders.Single(o => o.Id = id);
   return View(viewModel);
}

This wouldn't throw if Id is the unique per order, because there is only a single match (not many). Your view could then have something like:

<ul>
<% foreach (OrderDetails od in Model.OrderDetails) { %>
   <li><%: od.UnitPrice %> (Or whatever information you wanted to show) </li>
<% } %>
</ul>

I'm assuming you would be using a strongly typed view of type Order, otherwise you'd have to work with ViewData, but it looks from your question like you're happy enough with those concepts already.

Edit - adding more...

1.The typing of your page is causing you some problems, make sure you are clear in your own mind exactly what your Model is. If you are passing in a list - like you would in an Index action - you need a page that inherits ViewPage> (you can see this in the <%@ Page %> declaration at the top of the page). If you're going to write code like "for each... in model", that would imply that your model must contain more than one thing. This is where your "GetEnumerator" error message is from.

Your view as posted inherits ViewPage, ie the model is a single object, not a collection of objects, and so "for each ... in model" has no sensible meaning. The type of your View should be the same as the type being passed down by your controller. Your Index method passes a List, and List is an example of an IEnumerable. Your details however passes a single YourModelClass.

2.The error message "Compiler Error Message: CS1061: 'ss.Models.OrderDetail' does not contain a definition for 'OrderDetails'" - check your model, if there are relationships (foreign keys etc) between your tables, they should be joined on the model diagram, and you'd normally have navigation properties as well. The fact that you're getting this message means that something in that isn't there.

3.I'd suggest it might be worth checking out some of the videos, as the explanations are quite handy. Try some of the videos at http://www.asp.net/mvc/fundamentals . I Joe Stagner's "For the rest of us" series are very good, and as a starting point Stephen Walther's "Creating a Movie DB Application" would help, as it shows this kind of thing.