Question

以下代码引发了 System.ServiceModel.CommunicationException 。它正在调用一个名为 Login 的WCF服务操作，它返回一个EF4 POCO：

        var client = new AuthServiceReference.AuthServiceClient();

        try
        {
            Console.Write("Trying to logon...");
            var session = client.Login("user", "password"); // throws CommunicationException
            Console.WriteLine("done!");
            Console.WriteLine("Session ID: {0}. Expires {1}", 
                session.Id, session.UtcExpires.ToLocalTime());
        }
        finally
        {
            client.Close();
        }

我一直在调试＆amp;寻找数小时试图找出为什么这种情况发生了如何解决它。到目前为止我发现了什么：

这可能是序列化问题
当我从 Session 类的 Owner 成员中删除 DataMemberAttribute 时，异常消失，但这意味着它不会被序列化。

如果有人能对这个问题有所了解，我将不胜感激。

以下是服务合同的代码＆amp; POCO课程：

[ServiceContract]
public interface IAuthService
{
    [OperationContract]
    Session Login(string username, string passwordHash);

    [OperationContract]
    void Logout(Guid sessionId);
}

[DataContract]
public class Session
{
    [DataMember]
    public Guid Id { get; set; }

    [DataMember]
    public DateTime UtcCreated { get; set; }

    [DataMember]
    public DateTime UtcExpires { get; set; }

    [DataMember] // serializes correctly if commented out
    public virtual User Owner { get; set; }

    public static Session Create(User owner)
    {
        return new Session
        {
            Owner = owner,
            Id = Guid.NewGuid(),
            UtcCreated = DateTime.UtcNow,
            UtcExpires = DateTime.UtcNow.AddDays(1)
        };
    }
}

[DataContract]
public class User
{
    [DataMember]
    public int Id { get; set; }

    [DataMember]
    public string Name { get; set; }

    [DataMember]
    public string PasswordHash { get; set; }

    [DataMember]
    public string PasswordSalt { get; set; }

    [DataMember]
    public bool IsContributor { get; set; }

    [DataMember]
    public bool IsConfirmed { get; set; }

    [DataMember]
    public bool IsAdmin { get; set; }

    [DataMember]
    public string Email { get; set; }

    [DataMember]
    public virtual ICollection<Post> Posts { get; set; }

    [DataMember]
    public virtual ICollection<Comment> Comments { get; set; }
}

Answer 1

当使用WCF序列化POCO代理时，这是一个已知问题。有一个MSDN walkthough解释了如何使用 System.Data.Objects.ProxyDataContractResolver 来解决它。

基本上，您创建一个名为 ApplyDataContractResolverAttribute 的新类，并将其应用于返回POCOS的服务方法：

[ServiceContract]
public interface IAuthService
{
    [OperationContract]
    [ApplyDataContractResolver]
    Session Login(string username, string passwordHash);
}

using System;
using System.Data.Objects;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;

namespace WcfExampleBlog.Services
{
    public class ApplyDataContractResolverAttribute : Attribute, IOperationBehavior
    {
        #region IOperationBehavior Members

        public void AddBindingParameters(OperationDescription description, BindingParameterCollection parameters)
        {
        }

        public void ApplyClientBehavior(OperationDescription description, ClientOperation proxy)
        {
            var dataContractSerializerOperationBehavior =
                description.Behaviors.Find<DataContractSerializerOperationBehavior>();
            dataContractSerializerOperationBehavior.DataContractResolver =
                new ProxyDataContractResolver();
        }

        public void ApplyDispatchBehavior(OperationDescription description, DispatchOperation dispatch)
        {
            var dataContractSerializerOperationBehavior =
                description.Behaviors.Find<DataContractSerializerOperationBehavior>();
            dataContractSerializerOperationBehavior.DataContractResolver =
                new ProxyDataContractResolver();
        }

        public void Validate(OperationDescription description)
        {
            // Do validation.
        }

        #endregion
    }
}

Answer 2

我假设'User'类是自定义类？如果是这样，您需要在ServiceContract属性下面添加它：

[KnownType(typeof(User))]

您还需要在User类上设置[DataMember]和[ServiceContract]属性。

从WCF服务操作返回EF4 POCO时引发的CommunicationException

2 个答案: