尝试使用 DataContractJsonSerializer 反序列化 JSON 时出错

Question

这个真的把我难住了。我正在尝试反序列化从 ASP.NET Web 服务获得的以下 JSON 字符串：

"{\"d\":{\"__type\":\"KPCServer.LogonResult\",\"User\":{\"UserId\":\"affaa328-5b53-430e-991a-22674ede6faf\",\"Email\":\"test@test.com\",\"Alias\":\"Mike\",\"FullName\":\"Mike Christensen\",\"Password\":\"secret\",\"Location\":\"Redmond, WA\",\"ImageUrl\":null,\"DateOfBirth\":\"\\/Date(-62135568000000)\\/\",\"LastLogon\":\"\\/Date(1350450228000)\\/\",\"UserSince\":\"\\/Date(1197980020000)\\/\",\"MailingList\":true,\"Bio\":\"Test\"},\"NewUser\":false,\"Ticket\":\"FJEjfje87fjef88fe8FAF8fA88fAjk+AFJ9fja9Fa9Ff99aJF9aFjfA99fjaBFJ7zqmlcHn9Dfw=\"}}"

我有以下几种：

public class User
{
   public Guid UserId { get; set; }
   public string Email { get; set; }
   public string Alias { get; set; }
   public string FullName { get; set; }
   public string Password { get; set; }
   public string Location { get; set; }
   public string ImageUrl { get; set; }
   public DateTime DateOfBirth { get; set; }
   public DateTime LastLogon { get; set; }
   public DateTime UserSince { get; set; }
   public bool MailingList { get; set; }
   public string Bio { get; set; }
}

[DataContract(Name="KPCServer.LogonResult")]
public class LogonResult
{
   [DataMember] public User User { get; set; }
   [DataMember] public bool NewUser { get; set; }
   [DataMember] public string Ticket { get; set; }
}

[DataContract]
[KnownType(typeof(LogonResult))]
public class Result<T>
{
   [DataMember]
   public T d { get; set; }
}

然后我尝试使用以下方法反序列化字符串：

using (MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(json)))
{
   DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Result<T>));
   Result<T> result = serializer.ReadObject(stream) as Result<T>;

   return result.d;
}

注意：在上述方法中，T 的类型为LogonResult。

但是，我在ReadObject 上遇到以下异常：

System.Runtime.Serialization.SerializationException was unhandled by user code
  HResult=-2146233076
  Message=JSON contains a '__type' member specifying the data contract name ':KPCServer.LogonResult'. The deserializer has no knowledge of any type that maps to this contract. Add the type corresponding to 'KPCServer.LogonResult' to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding it to the list of known types passed to DataContractSerializer. You can also often eliminate this error by avoiding the use of derived types where the JSON is produced.
  Source=System.ServiceModel.Web
  InnerException: 

如果我跑：

json = json.Replace("_type", "_blah");

然后一切正常。这是在 Windows Phone 8 上使用 Silverlight。

Answer 1

这是因为：

"\"__type\":\"KPCServer.LogonResult\""

不包含数据协定命名空间。这可以通过修改LogonResult 上的DataContractAttribute 来解决：

[DataContract(Name = "KPCServer.LogonResult", Namespace="")]
public class LogonResult
{
    [DataMember]
    public User User { get; set; }
    [DataMember]
    public bool NewUser { get; set; }
    [DataMember]
    public string Ticket { get; set; }
}