ICollection <T> 为什么在HashSet上调用SerializationBinder <T> 但不在清单上 <T>

Question

I have an object like this :

public class MyCollec
{
    public ICollection<MyObject> MyCollection { get; set; }

    public MyCollec()
    {
        MyCollection = new List<MyObject>();
    }
}

In WebApi i had a SerializationBinder, in my webApiConfig :

jsonFormatter.SerializerSettings.Binder = new DefaultSerializationBinder();

When I call my controller that return my all object i get a structure like this

{
  "MyCollection": [
    {
        ...
    },
    {
        ...
    }
  ]
}

But if i change my constructor with an hashset

public MyCollec()
{
    MyCollection = new HashSet<MyObject>();
}

The result of my controller is like this :

{
  "MyCollection": {
    "$type": "System.Collections.Generic.HashSet`1[[WebApplication1.Models.MyObject, WebApplication1]], System.Core",
    "$values": [
            {
                ...
            },
            {
                ...
            }
        ]
    }
}

I would like understand why ? What is the difference which induce this behavior ?

Is-it possible to use a HashSet but give the same result like with the list ?

EDIT :

@Grundy comment :

TypeNameHandling property is Auto and from doc: Include the .NET type name when the type of the object being serialized is not the same as its declared type. So seems HashSet serialized is not the same as its declared type.

It's true, it's the reason, but why it's not true for List ? The type is different of ICollection like HashSet...

Moreover, I try to change TypeNameHandling property but there no option for set $type only on inherited objects...

http://www.newtonsoft.com/json/help/html/T_Newtonsoft_Json_TypeNameHandling.htm

Answer 1

Thanks to @Grundy for the clue.

I keep

jsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.Auto;

and I had a custom JsonConverter to change the serialization of HashSet

public class HashSetArrayConverter : JsonConverter
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        IEnumerable collectionObj = (IEnumerable)value;

        writer.WriteStartObject();

        foreach (object currObj in collectionObj)
        {
            serializer.Serialize(writer, currObj);
        }

        writer.WriteEndObject();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        return serializer.Deserialize(reader, objectType);
    }

    public override bool CanConvert(Type objectType)
    {
        var canConvert = IsAssignableToGenericType(objectType, typeof(HashSet<>));
        return canConvert;
    }

    private static bool IsAssignableToGenericType(Type givenType, Type genericType)
    {
        var interfaceTypes = givenType.GetInterfaces();

        if (interfaceTypes.Any(it => it.IsGenericType && it.GetGenericTypeDefinition() == genericType))
        {
            return true;
        }

        if (givenType.IsGenericType && givenType.GetGenericTypeDefinition() == genericType)
            return true;

        Type baseType = givenType.BaseType;
        if (baseType == null) return false;

        return IsAssignableToGenericType(baseType, genericType);
    }
}

and add it in config :

jsonFormatter.SerializerSettings.Converters.Add(new HashSetArrayConverter());