Problems with Silverlight DataContractJsonSerializer.

Monday, March 16 2009

I don’t think I am a patient developer, I do know good developers and they are very patient people that will discover the issues and find what’s the best solution. I write code fast and I expect everything to work, I spend my time in design so if something that I didn’t anticipate does not work for an unknown limitation, I get very frustrated. Last week I had to use the DataContractJsonSerializer. No problem I thought as I have used before the XML serializer.

For the Silverlight communication this is the class you want to use.

The class is on the namespace:

using System.Runtime.Serialization.Json;

 

Yet make sure the System.ServiceModel.Web.dll is referenced. This would be my first question.

Using primitive objects for some reason that I haven’t discovered yet gives me this exception below:

Testing' is not a valid JSON primitive. This error can also occur when extraneous data is present after the JSON data."

            string obj = "test";
            MemoryStream memoryStream = new MemoryStream();
            DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
            serializer.WriteObject(memoryStream, obj);
            memoryStream.Position = 0;
            StreamReader streamReader = new StreamReader(memoryStream);
            string JSON = streamReader.ReadToEnd();
            memoryStream.Close();
 

Now using generics I get this exception for some another weird reason:

System.MissingMethodException was unhandled by user code
  Message="Method not found: 'Boolean System.Runtime.Serialization.DataContract.get_IsReference()'."
  Source="System.ServiceModel.Web"

Looking at the web, I found many other people with issues using that class. I should spend some time this weekend and debug that class to see what the problems might be or if I’m misusing it, yet I accomplish to get it working for now. After the projects that I am in a rush to finish, I promise I’ll go back and debug it to find where those exceptions.

Thanks Richie Carmichael for sending me a sample of a good use for the class.

Those are links from the forums with similar issues with the DataContractJsonSerializer class:

http://social.msdn.microsoft.com/forums/en-US/csharpgeneral/thread/37558154-88a9-41f0-a9d6-a2cb4052a5ce/

http://pietschsoft.com/post/2008/08/NET-35-SP1-DataContractJsonSerializer-Bug.aspx

http://pietschsoft.com/post/2008/02/NET-35-JSON-Serialization-using-the-DataContractJsonSerializer.aspx

Tagged as: , ,

Comments

Morten said on 3.18.2009 at 11:40 PM

Also note that if you try to deserialize more than 2mb of JSON data you will get a similar exception, unless you change the MaxLength property.

Efim said on 5.14.2009 at 2:46 PM

You have to use the [DataContract] and [DataMember] attributes on your data:

[DataContract]

public class MyData

{

public MyData()

{

this.Children = new List<MyData>();

}

[DataMember]

public string Name { get; set; }

[DataMember]

public string Value { get; set; }

[DataMember]

public List<MyData> Children { get; set; }

}