Type descriminator for dictionary value by key

[dazinator]

I'd like to deserialize some yaml into a type that has a polymorphic dictionary property.
I'd like to implement a scheme where by, when deserializing dictionary<string, BaseType> I'd like to select the concrete type based on the dictionary key value.

It's not just a straight forward mapping however- I need to run some logic on the key value.

propertyA: foo
  myDictionary:
    objectOne@typeA:
        foo: bar
    objectTwo@typeB
        bar:  bat
    

So here I my type has a property called MyDictionary which is a Dictionary<string, BaseType>. I'd like to analyse / map the value of the key after the @ to work out what type should be selected for deseriliazation. Is this possible?

The docs suggest it may not be.

[dazinator]

The desire for this is that:

• I want to use a dictionary to ensure there cannot be duplicate keys added by the user.
• • I want to use polymorphism so I can extend the subtypes to support different planned features.
• I want to include the type descriminator in the key because I see this as part of the identity of the object, e.g adding two items to the dictionary with the same name but different types should be allowed hence the type + name should be part of the key.. without this, this would not be valid:

propertyA: foo
  myDictionary:
    foo:
        type: typeA
        foo: bar
    foo:
        type: typeB
        bar:  bat

I want that to be valid so I want the type as part of the key:

propertyA: foo
  myDictionary:
    foo@typeA:
        foo: bar
    foo@typeB:
        bar:  bat

Now there is no problem.
I could ofcourse still use this "foo@typeA" convention but if I cant use it for type descriminator then I'd have to repeat the type as a property also to support type descriminator and this is just added room for errors and seems like undesirable repetition:

propertyA: foo
  myDictionary:
    foo@typeA:
        type: typeA
        foo: bar
    foo@typeB:
        type: typeB
        bar:  bat

[EdwardCooke]

Your going to need to build your own type descriminator for that. They’re relatively easy to implement. I think you will be able to get at what you need to be able to do this.

[dazinator]

Thank you. I will delve into the existing extension method to configure type descrimination and see what I can work out. It will be a few days before I can do this, any pertinent information around implementation is most welcome otherwise I will update here if I solve it.

[dazinator]

I am guessing I would need to aim for something like this:

var deserializer = new DeserializerBuilder()
    .WithTypeDiscriminatingNodeDeserializer((o) =>
    {
        o.AddKeyValueTypeDiscriminator<KeyValuePair<string, TypeObject>>("Key", (keyValue)=>{
  return keyValue=="foo" ? typeof(FooType) : typeof(BarType) // whatever custom logic here
 });
    })
    .Build();