Not able to deserialize Lazy object

Question

I want to Serialize and DeSerialize an object which contains a Lazy Collection of some custom objects.

Normally everything works perfectly fine but, if namespaces of classes used for serialization are changed, then this issue occurs.

I have written a SerializationBinder to point to right classes while deserializing. But for some reason, I am not getting deserialized values.

Following code snippet explains the problem that I am getting;

Classes used for Serialization:

namespace ConsoleApplication14
{
    [Serializable]
    public class MyInnerClass : ISerializable
    {
        private string _stringInInnerClassKey = "StringInInnerClass";
        public string StringInInnerClass { get; set; }

        public MyInnerClass() { }

        private MyInnerClass(SerializationInfo info, StreamingContext context)
        {
            StringInInnerClass = info.GetString(_stringInInnerClassKey);
        }

        public void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            info.AddValue(_stringInInnerClassKey, StringInInnerClass);
        }
    }

    [Serializable]
    public class MyOuterClass : ISerializable
    {
        private string _collectionOfObjKey = "CollectionOfInnerObj";
        public Lazy<Collection<MyInnerClass>> CollectionOfInnerObj { get; set; }

        private MyOuterClass(SerializationInfo info, StreamingContext context)
        {
            if (info == null) throw new ArgumentNullException("serializationInfo");

            CollectionOfInnerObj =
                (Lazy<Collection<MyInnerClass>>)
                    info.GetValue(_collectionOfObjKey, typeof(Lazy<Collection<MyInnerClass>>));
        }

        public MyOuterClass() { }

        public void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            if (info == null) throw new ArgumentNullException();

            info.AddValue(_collectionOfObjKey, CollectionOfInnerObj, typeof(Lazy<Collection<MyInnerClass>>));
        }
    }
}

Above same classes are used for Deserialization but only namespace is changed to ConsoleApplication14.OtherNamespace

For such Deserialization to work, I have used following SerializationBinder class:

public class MyBinder : SerializationBinder
{
    public override Type BindToType(string assemblyName, string typeName)
    {
        if (assemblyName.Equals(
                "ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"))
        {
            if (typeName.Equals("ConsoleApplication14.MyOuterClass"))
                return typeof(ConsoleApplication14.OtherNamespace.MyOuterClass);

            if (typeName.Equals("ConsoleApplication14.MyInnerClass"))
                return typeof(ConsoleApplication14.OtherNamespace.MyInnerClass);
        }

        if (assemblyName.Equals("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"))
        {
            if (typeName.Equals(
                    "System.Collections.ObjectModel.Collection`1[[ConsoleApplication14.MyInnerClass, ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]"))
                return typeof(Collection<ConsoleApplication14.OtherNamespace.MyInnerClass>);

            if (typeName.Equals(
                    "System.Collections.Generic.List`1[[ConsoleApplication14.MyInnerClass, ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]"))
                return typeof(List<ConsoleApplication14.OtherNamespace.MyInnerClass>);

            if (typeName.Equals(
                    "System.Lazy`1[[System.Collections.ObjectModel.Collection`1[[ConsoleApplication14.MyInnerClass, ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]"))
                return typeof(Lazy<Collection<ConsoleApplication14.OtherNamespace.MyInnerClass>>);

            //I THINK, MAYBE THIS 'IF' CONDITION IS THE PROBLEM, BUT DONT KNOW HOW TO FIX THIS.
            if (typeName.Equals(
                    "System.Lazy`1+Boxed[[System.Collections.ObjectModel.Collection`1[[ConsoleApplication14.MyInnerClass, ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]"))
                return typeof(Lazy<Collection<ConsoleApplication14.OtherNamespace.MyInnerClass>>);
        }

        return Type.GetType(String.Format("{0}, {1}", typeName, assemblyName));
    }
}

Serialization and Deserialization of object of MyCustomClass:

public static void Main(string[] args)
    {
        //----------------Object Creation----------------------
        var objToSerialize = new MyOuterClass
                             {
                                 CollectionOfInnerObj =
                                     new Lazy<Collection<MyInnerClass>>(
                                     () => new Collection<MyInnerClass>
                                           {
                                               new MyInnerClass
                                               {
                                                   StringInInnerClass = "a"
                                               },
                                               new MyInnerClass
                                               {
                                                   StringInInnerClass = "aa"
                                               },
                                           })
                             };
        //------------------------------------------------------

        //---------------------Serialization---------------------
        using (var stream = File.Create("E:\\tempFile.tmp"))
        {
            var binaryFormatter = new BinaryFormatter();

            binaryFormatter.Serialize(stream, objToSerialize);

            stream.Close();
        }
        //------------------------------------------------------

        //-------------------DeSerialization--------------------
        using (var stream = File.OpenRead("E:\\tempFile.tmp"))
        {
            var binaryFormatter = new BinaryFormatter {Binder = new MyBinder()};
            var objOfOtherNamespaceClass = (OtherNamespace.MyOuterClass) binaryFormatter.Deserialize(stream);

            //Getting NullReferenceException when Value property of objOfOtherNamespaceClass.CollectionOfInnerObj is called
            foreach (OtherNamespace.MyInnerClass stringVal in objOfOtherNamespaceClass.CollectionOfInnerObj.Value)
                Console.WriteLine(stringVal.StringInInnerClass);

            stream.Close();
        }
        //-----------------------------------------------------
    }

I am getting NullReferenceException when Value property of deserialized Lazy object is called. (i.e. when objOfOtherNamespaceClass.CollectionOfInnerObj.Value is called)

Please help me resolve this issue...

Subject

I remember, the BinaryFormatter with ISurrogate had a bug when circular dependency was in (de)serialized graph and there was not intent to fix that. I'm not sure, but this behaviour looks similar. – Cattle

Answer 1

Problem is in line already highlighted by you

//I THINK, MAYBE THIS 'IF' CONDITION IS THE PROBLEM, BUT DONT KNOW HOW TO FIX THIS.
            if (typeName.Equals(
                    "System.Lazy`1+Boxed[[System.Collections.ObjectModel.Collection`1[[ConsoleApplication14.MyInnerClass, ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]"))
                return typeof(Lazy<Collection<ConsoleApplication14.OtherNamespace.MyInnerClass>>);

Please change this code to following

if (typeName.Equals(
                "System.Lazy`1+Boxed[[System.Collections.ObjectModel.Collection`1[[ConsoleApplication14.MyInnerClass, ConsoleApplication14, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]"))
{
    return Type.GetType(typeName.Replace("ConsoleApplication14.MyInnerClass", "ConsoleApplication14.OtherNamespace.MyInnerClass"));
}

Type should be Boxed class, declared inside Lazy source code

public class Lazy<T>
{

    #region Inner classes
    /// <summary>
    /// wrapper class to box the initialized value, this is mainly created to avoid boxing/unboxing the value each time the value is called in case T is 
    /// a value type
    /// </summary>
    [Serializable]
    class Boxed
    {
        internal Boxed(T value)
        {
            m_value = value;
        }
        internal T m_value;
    }

Hope this help.

Hilliary