使用ReferenceLoopHandling.Ignore序列化依赖于循环的ISerializable对象时，抛出StackOverflowException。

Question

我有一个使用二进制序列化来保留数据的旧版应用程序。现在，我们想使用Json.net 4.5在不对现有类进行太多更改的情况下序列化数据。

事情一直很好，直到我们遇到了循环依赖类。有解决此问题的解决方法吗？

示例代码如下所示

[Serializable]
class Department : ISerializable
{
    public Employee Manager { get; set; }
    public string Name { get; set; }

    public Department() { }
    public Department( SerializationInfo info, StreamingContext context )
    {
        Manager = ( Employee )info.GetValue( "Manager", typeof( Employee ) );
        Name = ( string )info.GetValue( "Name", typeof( string ) );
    }
    public void GetObjectData( SerializationInfo info, StreamingContext context )
    {
        info.AddValue( "Manager", Manager );
        info.AddValue( "Name", Name );
    }
}

[Serializable]
class Employee : ISerializable
{
    [NonSerialized] //This does not work
    [XmlIgnore]//This does not work
    private Department mDepartment;
    public Department Department
    {
        get { return mDepartment; }
        set { mDepartment = value; }
    }

    public string Name { get; set; }

    public Employee() { }
    public Employee( SerializationInfo info, StreamingContext context )
    {
        Department = ( Department )info.GetValue( "Department", typeof( Department ) );
        Name = ( string )info.GetValue( "Name", typeof( string ) );
    }

    public void GetObjectData( SerializationInfo info, StreamingContext context )
    {
        info.AddValue( "Department", Department );
        info.AddValue( "Name", Name );
    }
}

和测试代码

Department department = new Department();
department.Name = "Dept1";

Employee emp1 = new Employee { Name = "Emp1", Department = department };
department.Manager = emp1;

Employee emp2 = new Employee() { Name = "Emp2", Department = department };
IList<Employee> employees = new List<Employee>();
employees.Add( emp1 );
employees.Add( emp2 );

var memoryStream = new MemoryStream();
var formatter = new BinaryFormatter();
formatter.Serialize( memoryStream, employees );

memoryStream.Seek( 0, SeekOrigin.Begin );
IList<Employee> deserialisedEmployees = formatter.Deserialize( memoryStream ) as IList<Employee>; //Works nicely

JsonSerializerSettings jsonSS= new JsonSerializerSettings();
jsonSS.TypeNameHandling = TypeNameHandling.Objects;
jsonSS.TypeNameAssemblyFormat = FormatterAssemblyStyle.Full;
jsonSS.Formatting = Formatting.Indented;
jsonSS.ReferenceLoopHandling = ReferenceLoopHandling.Ignore; //This is not working!!
//jsonSS.ReferenceLoopHandling = ReferenceLoopHandling.Serialize; //This is also not working!!
jsonSS.PreserveReferencesHandling = PreserveReferencesHandling.All;
string jsonAll = JsonConvert.SerializeObject( employees, jsonSS ); //Throws stackoverflow exception

Edit1
：该问题已报告给Json（http://json.codeplex.com/workitem/23668）

Edit2 ：序列化在版本4.5 R11中可以正常工作，但是反序列化仍然不起作用

Edit3 ：当循环引用对象不为null时，实际上序列化本身不起作用

Edit4 ：来自Json.net问题库的评论是问题在您的末端，并已解决问题。但是我找不到我的代码出了什么问题。我对此发布了另一个

Answer 1

我想你会需要同时ReferenceLoopHandling.Serialize和PreserveReferencesHandling.All复制二进制序列化的行为。但是，生成的JSON可能不那么漂亮。

编辑： 我对JSON.Net4.5r10进行了更深入的研究，发现了一个缺陷：JsonSerializerInternalWriter不检查#ShouldWriteReference通过获得的引用ISerializable。

随着foreach循环中#SerializeISerializable，如下改写，你的对象图顺利往返。

  foreach (SerializationEntry serializationEntry in serializationInfo)
  {
    writer.WritePropertyName(serializationEntry.Name);
    var entryValue = serializationEntry.Value;
    var valueContract = GetContractSafe(entryValue);
    if (ShouldWriteReference(entryValue, null, valueContract, null, member))
    {
      WriteReference(writer, entryValue);
    }
    else
    {
      SerializeValue(writer, entryValue, valueContract, null, null, member);
    }
  }