WCF和Silverlight之间的序列化

Question

I need an expert's help. I have a custom class called MyException. The purpose of this class is to log exceptions with custom information. The definition of this class is as shown here:

[DataContract]
public class MyException
{
  [DataMember]
  public string StackTrace { get; set; }

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

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

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

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

  public MyException() 
  {}

  public MyException(string message)
  {
    this.Message = message;
  }

  public MyException(string message, string stackTrace)
  {
    this.Message = message;
    this.StackTrace = stackTrace;
  }
}

I have a WCF service that is intended to accept a MyException in JSON format and write it's contents to a database. Because of the amount of information I intend to track, I need to use a POST operation, so I decided to base my implementation off this blog post . My service description can be found here:

[OperationContract]
[WebInvoke(UriTemplate="/LogError", Method="POST", BodyStyle = WebMessageBodyStyle.Bare, RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
public string LogError(Stream stream)
{
  try
  {
    DataContractJsonSerializer serializer = 
      new DataContractJsonSerializer(typeof(MyException));
    MyException exception = (MyException)(serializer.ReadObject(stream));
    // Write the exception details to the database
  }
  catch (Exception ex)
  {
    // Write the exception details to the database
  }
}

[OperationContract]
public void Test(MyException exception)
{ }

I added the "Test" operation so that the MyException would be exposed during proxy generation to my Silverlight application. My Silverlight application attempts to post to LogError using the following code:

MyServiceProxy.MyException exception = new MyServiceProxy.MyException();
exception.Message = e.Error.Message;
exception.StackTrace = e.Error.StackTrace;
exception.Component = GetComponentName();
exception.TypeName = e.Error.FullName;

string json = string.Empty;
using (MemoryStream stream = new MemoryStream())
{
  DataContractJsonSerializer serializer = new 
    DataContractJsonSerializer(typeof(MyServiceProxy.MyException));
  serializer.WriteObject(stream, exception);

  stream.Position = 0;
  using (StreamReader reader = new StreamReader(stream))
  {
    json = reader.ReadToEnd();
  }

  Uri uri = new Uri("/myService.svc/LogError", UriKind.Absolute);
  WebClient myService = new WebClient();
  myService.UploadStringCompleted += 
    new UploadStringCompletedEventHandler(myService_UploadStringCompleted);
  myService.Headers["Content-type"] = "application/x-www-form-urlencoded";
  myService.Encoding = Encoding.UTF8;
  myService.UploadStringAsync(uri, "POST", json);
}

When I run this code, I get an error in my Silverlight app that says: "Type 'MyServiceProxy.MyException' with data contract name 'MyException:http://schemas.datacontract.org/2004/07/MyNamespace' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer."

What am I doing wrong?

Answer 1

You specify in the request that the content-type of the request is "application/x-www-form-urlencoded". But the content is actually JSON (generated using the DataContractJsonSerializer ). Try updating the content-type to the correct one ("application/json") and that should get you further where you need to be.

Answer 2

I believe the issue here is that your type is different, you are using the proxy class and serializing it, and then trying to deserialize it as a different type when you get it back on the server side.

You should be able to add the KnownType attribute, I believe this would be needed on the auto generated proxy class.

Answer 3

Maybe if you explicitly set the namespace on the DataContract attribute. Something like [DataContract(Namespace = "http://tempuri.org/2010/etc")] so the serializer would treat the classes as being the same.

I would give it a try. Adding the namespace and regenerating the reference.