public interface IA
{
    IB InterfaceB { get; set;  }
}

public interface IB
{
    IA InterfaceA { get; set;  }

    void SetIA(IA value);
}

[Serializable]
public class ClassA : IA
{
    public IB InterfaceB { get; set; }

    public ClassA()
    {
        // Call outside function to get Interface B
        IB interfaceB = Program.GetInsanceForIB();

        // Set IB to have A
        interfaceB.SetIA(this);
    }
}

[Serializable]
public class ClassB : IB
{
    public IA InterfaceA { get; set; }

    public void SetIA(IA value)
    {
        this.InterfaceA = value as ClassA;
    }
}

public interface IA
{
    IB InterfaceB { get; set; }
}

public interface IB
{
    IA InterfaceA { get; set; }
    void SetIA(IA value);
}

[Serializable]
public class ClassA : IA
{
    public IB InterfaceB { get; set; }

    public ClassA()
    {
        // Call outside function to get Interface B
        this.InterfaceB = new ClassB();

        // Set IB to have A
        InterfaceB.SetIA(this);
    }
}

[Serializable]
public class ClassB : IB
{
    public IA InterfaceA { get; set; }

    public void SetIA(IA value)
    {
        this.InterfaceA = value;
    }
}

[STAThread]
static void Main()
{
    MemoryStream ms = new MemoryStream();
    BinaryFormatter bin = new BinaryFormatter();

    ClassA myA = new ClassA();

    bin.Serialize(ms, myA);

    ms.Position = 0;

    ClassA myOtherA = bin.Deserialize(ms) as ClassA;


    Console.ReadLine();
}

[NonSerialized]

[Serializable]
public class ClassB : IB, ISerializable
{
  public IA InterfaceA { get; set; }

  public void SetIA(IA value)
  {
     this.InterfaceA = value as ClassA;
  }

  private MyStringData(SerializationInfo si, StreamingContext ctx) {
    Type interfaceAType = System.Type.GetType(si.GetString("InterfaceAType"));
    this.InterfaceA = si.GetValue("InterfaceA", interfaceAType);
  }

  void GetObjectData(SerializationInfo info, StreamingContext ctx) {
    info.AddValue("InterfaceAType", this.InterfaceA.GetType().FullName);
    info.AddValue("InterfaceA", this.InterfaceA);
  }
}

[Serializable]
public class ClassA : IA
{
    private IB _interfaceB;
    public IB InterfaceB { get { return _interfaceB; } set { _interfaceB = value; } }

    public ClassA()
    {
        // Call outside function to get Interface B
        IB interfaceB = Program.GetInsanceForIB();

        // Set IB to have A
        interfaceB.SetIA(this);
    }
}

[Serializable]
public class ClassB : IB
{
    private IA _interfaceA;
    public IA InterfaceA { get { return _interfaceA; } set { _interfaceA = value; } }

    public void SetIA(IA value)
    {
        this.InterfaceA = value as ClassA;
    }
}