Object serialization trouble (c#)

Question

Dear Stack Overflow community, I thought I'd never have to ask this question, but apparently something is going wrong with serialization or my usage of it.

I have a class which I need to serialize:

[Serializable]
public class Device : ISerializable, IDisposable
{
   public delegate void ListChangedEventHandler(object sender, ListChangedEventArgs e);
   public string Name { get; set; }
   public string Description { get; set; }
   public string IPAddress { get; set; }

   [Browsable(false)]
   public ThreadSafeBindingList<Item> Items { get; set; }

    [Browsable(false)]
    public MibEntity AssociatedMibEntity { get; set; }
 
    //methods etc.
}

A little explanation:

ThreadSafeBindingList is inherited from System.ComponentModel.BindingList MibEntity is a class of SharpSNMP library (https://sharpsnmp.com/)

Problem: When I try to deserialize the object, MibEntity is always null. Other properties are fine. MibEntity class is in external dll, which I reference in the project where Device class resides.

This is its content:

[Serializable]
public class MibEntity 
{
    public MibEntity()
    {
        Children = new List<MibEntity>(); 
    } 
    
    [Browsable(false)]
    public List<MibEntity> Children { get; set; }

    [Browsable(true)]
    [Category("General")]
    public string OID { get; set; }

    private string _name;
    [Browsable(true)]
    [Category("General")]
    public string Name
    {
        get { return _name; }
        set { _name = value; }
    }

    [Browsable(true)]
    public string Description { get; set; }

    [Browsable(false)]
    public int Value { get; set; }


    [Browsable(true)]
    public AccessType AccessType { get; set; } //this is enum from SharpSNMP library

    [Browsable(true)]
    public Status Status { get; set; } //this is enum from same assembly as this class

    [Browsable(true)]
    public string Syntax { get; set; }

    [Browsable(true)]
    public bool IsTableEntry { get; set; }

    [Browsable(true)]
    public IDefinition IDefinition { get; set; } //this is interface from SharpSNMP library
}

I use BinaryFormatter for serialization and deserialization. Thank you for your help!

Since you have custom serialization via ISerializable, we would need to see both the custom GetObjectData method and the custom deserialization constructor. — Marc Gravell
– Marc Gravell, Commented Aug 19, 2013 at 8:28

Marc Gravell · Accepted Answer · 2013-08-19 08:38:23Z

This invariably means you have made an error in your custom ISerializable implementation; the following works fine:

protected Device(SerializationInfo info, StreamingContext context)
{
    Name = info.GetString("Name");
    //...
    AssociatedMibEntity = (MibEntity)info.GetValue(
        "AssociatedMibEntity", typeof(MibEntity)); 
}
void ISerializable.GetObjectData(
    SerializationInfo info, StreamingContext context)
{
    info.AddValue("Name", Name);
    //...
    info.AddValue("AssociatedMibEntity", AssociatedMibEntity);
}

with validation:

using (var ms = new MemoryStream())
{
    var bf = new BinaryFormatter();
    bf.Serialize(ms, new Device {
        AssociatedMibEntity = new MibEntity { Name = "Foo"}});
    ms.Position = 0;
    var clone = (Device)bf.Deserialize(ms);
    Console.WriteLine(clone.AssociatedMibEntity.Name); // Foo
}

However, unless there is a good reason to implement ISerializable, you might be better served by simply removing your ISerializable implementation completely - noting that this will be a breaking change (any existing data won't deserialize correctly if you do this).

[Serializable]
public class Device : IDisposable // <=== no ISerializable; also removed
                                  // GetObjectData and custom .ctor

Also: my usual rant: BinaryFormatter might not be your best bet if you are storing this data anywhere. It is... brittle. There are a range of far more reliable serializers.

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