OData 服务不返回自定义对象

Question

这是我想要做的：

1. 我有一个现有的数据库，我需要从其中获取数据。

2. 我使用实体框架创建了数据协定以将它们映射到相应的表。在我的示例中，我有三个表 - tblOrder、tblProduct 和 tblCustomer。因此，我创建了三个数据契约来映射到这些表。实体框架注释已添加到数据协定中。我编写了一个单元测试来测试我的数据契约。通过直接实体框架调用，一切都按预期工作。请参阅下面的单元测试 1。

3. 为每个数据协定添加了 DataServiceKey 注释。并通过添加订单上下文和数据服务 svc 用 OData 服务包装它们。请参阅下文。

4. 编写了一个单元测试以通过 OData 服务访问一些现有订单数据。问题：OData 服务仅返回 Order 对象上的非自定义数据类型。它在客户数据类型字段（例如 CustomerInfo 和 ProductList）上返回 null。

我做错了什么吗？为了使 OData 调用能够处理使用 EF 进行检索的对象，我需要做些什么特别的事情吗？

---

[DataServiceKey("ID")]      
[Table("tblOrder", Schema = "schOnlineSale")]      
public class Order     
{     

     [Column("OrderId"), Key]        
     public int ID { get; set; }

     public string OrderName { get; set; }

     public int CustomerId { get; set; }

     [ForeignKey("CustomerId")]
     public virtual Customer CustomerInfo { get; set; }

     [ForeignKey("OrderId")]
     public virtual ICollection<Product> ProductList{ get; set; }
}

[DataServiceKey("CustomerId")]     
[Table("tblCustomer", Schema = "schOnlineSale")]     
public class Customer    
{

     [Key]
     public int CustomerId{ get; set; }

     [Column("FullName")]
     public string Name { get; set; }

     public string MailingAddress { get; set; }   
     public string City { get; set; }   
     public string State { get; set; }   
     public string ZIPCode { get; set; }   
}

[DataServiceKey("ProductId")]   
[Table("tblProduct", Schema = "schOnlineSale")]    
public class Product    
{

     [Key]
     public int ProductId{ get; set; }

     public int OrderId{ get; set; }

     public string ProductName { get; set; }

     public decimal SalePrice { get; set; }   
}

---

//OData Service wrapper classes    
public class OrderContext:  DbContext    
{        

     public DbSet<Order> Orders {get; set;}

     public DbSet<Product> Products {get; set;}
}

[ServiceBehavior(IncludeExceptionDetailInFaults = true)]   
public class OrderDataService : DataService<OrderContext>    
{

        // This method is called only once to initialize service-wide policies.
        public static void InitializeService(DataServiceConfiguration config)
        {
            config.SetEntitySetAccessRule("Orders", EntitySetRights.All);
            config.SetEntitySetAccessRule("Products", EntitySetRights.All);
            config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
            config.UseVerboseErrors = true;
        }

        protected override void HandleException(HandleExceptionArgs args)
        {
            try
            {
                args.UseVerboseErrors = true;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }

        protected override OrderContext CreateDataSource()
        {
            var dataSource = new OrderContext();
            dataSource.Configuration.ProxyCreationEnabled = false;
            return dataSource;            
        }
    }

---

//Unit Test 1 - Querying via data context directly
public void EFDataContext_GetOrderTest()
{            
    var context = new OrderContext();            
    var list = (from a in context.Orders 
          where a.OrderId == 10 || 
                a.OrderId == 15 ||
                a.OrderId== 20 select a).ToList();

    //CustomerInfo and ProductList values are populated properly
}


//Unit test 2 - Querying via OData Service
public void OData_GetOrderTest()
{
  string uriString = "http://localhost/OrderServices/OrderDataService.svc/Orders(10)";
  Uri serviceUri = new Uri(uriString);
  OrderContext context = new OrderContext(serviceUri);
  context.IgnoreResourceNotFoundException = true;
  var orderList = context.Orders;            

  foreach (Order s in orderList)
  {
     TestContext.WriteLine("OrderId=" + s.ID);

     Assert.IsNotNull(s.CustomerInfo);  //CustomerInfo is not returned with OData call
                                  //but it's returned properly with entity framework call.

     foreach (Product p in s.ProductList)
     {
        //ProductList is also not returned with OData Service call,
        //but it is returned properly when accessing through Entity Framework calls     
        //directly
     }

   }            
}

---

//app.config   
<configuration>    
  <connectionStrings>    
    <add name="OrderContext" connectionString="a valid connection string" providerName="System.Data.SqlClient" />    
  </connectionStrings>    
</configuration> 

Answer 1

OData（或在本例中为 WCF 数据服务客户端）不会延迟加载导航属性（这就是从关系创建的属性的名称）。你必须明确要求。

您可以通过 Expand 预先执行此操作，在其中您可以要求原始查询包含导航属性另一侧的实体。只需将 .Expand("Orders") 添加到您的查询中即可获取订单实体以及客户。

您也可以稍后通过 context.LoadProperty 方法执行此操作。