Same object got serialized twice in the object graph

[ekolis]

Once here:

"PrimaryRace": {
"$id": "22277",
"$type": "FrEee.Game.Objects.Civilization.Race, FrEee.Core",
"Name": "Random Race #2",
"PopulationIconName": null,
"NativeAtmosphere": "Methane",
"NativeSurface": "Ice",
"HappinessModelName": null,
"TraitNames": {
"$id": "22278",
"$type": "System.Collections.Generic.List1[[System.String, mscorlib]], mscorlib", "$values": [] }, "Aptitudes": { "$id": "22279", "$type": "FrEee.Utility.SafeDictionary2[[System.String, mscorlib],[System.Int32, mscorlib]], FrEee.Core",
"Physical Strength": 100,
"Intelligence": 100,
"Cunning": 100,
"Environmental Resistance": 100,
"Reproduction": 100,
"Happiness": 100,
"Aggressiveness": 100,
"Defensiveness": 100,
"Political Savvy": 100,
"Mining Aptitude": 100,
"Farming Aptitude": 100,
"Refining Aptitude": 100,
"Construction Aptitude": 100,
"Repair Aptitude": 100,
"Maintenance Aptitude": 100
},
"ID": 5212045564066541657,
"IsDisposed": false
},

And once here:

"Key": {
"$id": "22277",
"$type": "FrEee.Game.Objects.Civilization.Race, FrEee.Core",
"Name": "Random Race #2",
"PopulationIconName": null,
"NativeAtmosphere": "Methane",
"NativeSurface": "Ice",
"HappinessModelName": null,
"TraitNames": {
"$ref": "22278"
},
"Aptitudes": {
"$ref": "22279"
},
"ID": 5212045564066541657,
"IsDisposed": false
},

This is causing a crash on deserialization, because the object is defined twice. The sub-objects referenced by this object are being serialized properly, but the object itself is not.

I did do something special with this object to get it to deserialize in the first place - it was originally a key in a dictionary, but since JSON.NET doesn't support complex types for dictionary keys, I wrote a wrapper property, and marked the original dictionary property non-serializable:

/// <summary>
/// For serialization, since JSON.NET can't handle dictionary keys of complex types.
/// </summary>
public List<KeyValuePair<Race, long>> PopulationList
{
    get
    {
        return Population.ToList();
    }
    set
    {
        Population.Clear();
        foreach (var kvp in value)
            Population.Add(kvp);
    }
}

[ekolis]

I was able to work around this by changing the wrapper property:

/// <summary>
/// For serialization, since JSON.NET can't handle dictionary keys of complex types.
/// </summary>
public ISet<Tuple<Race, long>> PopulationList
{
    get
    {
        return new HashSet<Tuple<Race, long>>(Population.Select(kvp => Tuple.Create(kvp.Key, kvp.Value)));
    }
    set
    {
        Population.Clear();
        foreach (var t in value)
            Population.Add(t.Item1, t.Item2);
    }
}

[ekolis]

Well, not quite. The wrapper property isn't being serialized either now! Or rather, the tuples aren't... guess I'll need a custom type!

[ekolis]

Yeah, I was filtering out read-only properties, and since tuples are immutable...

[ekolis]

Nope, even a custom type didn't work. It appears that JSON.NET, when deserializing a property, first constructs a blank object, then assigns it to the property, then manipulates the property value. Which is completely useless if the property in question is a throwaway proxy for the real property, because this means that any changes that JSON.NET makes are thrown away! Maybe that's what type converters are for?

[ekolis]

This seems to be a bug with KeyValuePairs, because when I annotate my dictionary type with [JsonArray], I get the same duplicate-object problem. Perhaps this is because KeyValuePairs are structs?

[JamesNK]

ObjectCreationHandling.Replace

[ekolis]

Got a chance to look at this again, and no, this didn't help. The problem might be that the two references to my object are in two different dictionaries. So ObjectCreationHandling.Replace doesn't know that the other reference exists, perhaps?