【发布时间】：2013-07-30 20:44:35
【问题描述】：
新手，请多多包涵，因为我昨天刚开始使用 WCF。
我使用 Northwind 来获取数据，并且只在模型中添加了客户、订单、订单详细信息和产品，所以没什么特别的。
当我启动应用程序并调用 Test 并设置断点时，products 的值就在那里，并且它在没有错误的情况下完成。如果我随后尝试调用 GetMaxQuantityByOrderID(10248)，则会在底部列出错误。为什么 Test() 会起作用，而 WITHIN Test() 同样的方法不起作用？我什至添加了另一个（Test1()，与 Test 完全相同，只是它返回字符串：x.ProductName，正确显示 Queso Cabrales）。一个方法在另一个方法中被调用似乎很奇怪，但直接调用它会导致异常。
我遇到的另一个问题是 IEnumerable GetOrders() 仅在我添加 .ToList() 时才有效。没有它（或使用 .AsEnumerable()），我得到一个错误（ObjectContext 实例已被释放，不能再用于需要连接的操作。），即使设置了延迟加载错误。这背后的逻辑是什么？
IServiceTest.cs
using System.Collections.Generic;
using System.ServiceModel;
namespace WcfTestServiceLibrary
{
[ServiceContract]
public interface IServiceTest
{
[OperationContract]
IEnumerable<Orders> GetOrders();
[OperationContract]
IEnumerable<Customers> GetCustomers();
[OperationContract]
Customers GetCustomerByID(string customerID);
[OperationContract]
Orders GetOrderByID(int id);
[OperationContract]
IEnumerable<Order_Details> GetOrderDetailsByOrderID(int id);
[OperationContract]
Order_Details GetMaxQuantityByOrderID(int id);
[OperationContract]
void Test();
}
}
ServiceTest.cs
using System.Collections.Generic;
using System.Linq;
namespace WcfTestServiceLibrary
{
public class ServiceTest : IServiceTest
{
public IEnumerable<Orders> GetOrders()
{
using (var ctx = new NWEntities())
{
return (from o in ctx.Orders.Include("Order_Details.Products").Include("Customers")
select o).ToList();
}
}
public IEnumerable<Customers> GetCustomers()
{
using (var ctx = new NWEntities())
{
return (from c in ctx.Customers
select c);
}
}
public Customers GetCustomerByID(string customerID)
{
return (from c in GetCustomers()
where c.CustomerID == customerID
select c).FirstOrDefault();
}
public Orders GetOrderByID(int id)
{
IEnumerable<Orders> orders = GetOrders();
return (from o in orders
where o.OrderID == id
select o).FirstOrDefault();
}
public IEnumerable<Order_Details> GetOrderDetailsByOrderID(int id)
{
return GetOrderByID(id).Order_Details;
}
public Order_Details GetMaxQuantityByOrderID(int id)
{
Orders order = GetOrderByID(id);
return order == null ? null : order.Order_Details.OrderByDescending(x => x.Quantity).FirstOrDefault();
}
public void Test()
{
const int orderID = 10248;
var oq = GetMaxQuantityByOrderID(orderID);
var x = oq.Products;
}
}
}
错误：
An error occurred while receiving the HTTP response to http://localhost:8732/Design_Time_Addresses/WcfTestServiceLibrary/Service1/. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.
Server stack trace:
at System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException webException, HttpWebRequest request, HttpAbortReason abortReason)
at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)
at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.ClientReliableChannelBinder`1.RequestClientReliableChannelBinder`1.OnRequest(TRequestChannel channel, Message message, TimeSpan timeout, MaskingMode maskingMode)
at System.ServiceModel.Channels.ClientReliableChannelBinder`1.Request(Message message, TimeSpan timeout, MaskingMode maskingMode)
at System.ServiceModel.Channels.ClientReliableChannelBinder`1.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Security.SecuritySessionClientSettings`1.SecurityRequestSessionChannel.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
Exception rethrown at [0]:
at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
at IServiceTest.GetMaxQuantityByOrderID(Int32 id)
at ServiceTestClient.GetMaxQuantityByOrderID(Int32 id)
Inner Exception:
The underlying connection was closed: An unexpected error occurred on a receive.
at System.Net.HttpWebRequest.GetResponse()
at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)
Inner Exception:
Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.Net.Connection.SyncRead(HttpWebRequest request, Boolean userRetrievedStream, Boolean probeRead)
Inner Exception:
An existing connection was forcibly closed by the remote host
at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
【问题讨论】：
标签： wcf entity-framework