Question

I have a similar Problem to Serializing a HashSet

I have a Class with a Member of type Dictionary<String,HashSet<T>>

When i serialize the Object with BinaryFormatter, and then deserialize it, it comes up empty.

I don’t know how, or where to call the workaround posted here.

Any Hints? thanks in advance.

edit:
i tried to convert the hashset to a list, as one of the comments in the other thread suggested.

the object looks like this:

public class THashSet : HashSet<T> , ISerializable
{

    public THashSet(SerializationInfo info, StreamingContext context)
    {
        var list = (List<T>)info.GetValue("hashset", typeof(List<T>));     
        foreach (T t in list)
            this.Add(t);
    }

    public override void GetObjectData(SerializationInfo info,StreamingContext context)
    {
        info.AddValue("hashset", this.ToList<T>());
    }

when the object containing the THashSet is deserialized (and the constructor is called), the list is recovered correctly, as i see in the debugger.

but after the serializer is done, the object only contains an empty hashset.

Answer 1

Suppose for your T object you haven’t override methods GetHashCode and Equals. You need to do it.

UPD: All depends from your object implementation. And object is not so easy as you say. Your sitation, object:

[Serializable]
public class DataClass
{       
    public DataClass()
    {
    }

    public DataClass(string name, string description)
    {
        Name = name;
        Description = description;

        this.Dictionary = new Dictionary<string, HashSet<DataClass>>();
    }

    public string Name { get; set; }

    public string Description { get; set; }

    public Dictionary<string, HashSet<DataClass>> Dictionary { get; set; }
}

And serialization/deserialization code:

DataClass dataClass = new DataClass("name", "descr");
dataClass.Dictionary.Add("key1", new HashSet<DataClass>() { new DataClass("sample11", "descr11"), new DataClass("sample12", "descr12") });
dataClass.Dictionary.Add("key2", new HashSet<DataClass>() { new DataClass("sample21", "descr21"), new DataClass("sample22", "descr22") });
dataClass.Dictionary.Add("key3", new HashSet<DataClass>() { new DataClass("sample31", "descr31"), new DataClass("sample32", "descr32") });

byte[] serialized;
var formatter = new BinaryFormatter();

using (MemoryStream stream = new MemoryStream())
{
    formatter.Serialize(stream, dataClass);
    serialized = stream.ToArray();
}
using (MemoryStream streamDeserial = new MemoryStream())
{
    streamDeserial.Write(serialized, 0, serialized.Length);
    streamDeserial.Seek(0, SeekOrigin.Begin);
    var dictDeserial = formatter.Deserialize(streamDeserial) as DataClass;
} 

This code works well.