How to fallback to another deserialization attempt in case of exceptions?

[cdavernas]

Hello everyone!

I was wondering: is something like the following doable in the current state of YamlDotNet? If yes, any idea how? If no, what do you think could be reasonable alternatives?
The idea is to try deserializing an object with a given type, and if it fails, fallback to another type.

The problem with the following code is that when the t1 deserialization attempt fails, the t2 attempt will use the reader that has already moved forward (with the t1 attempt), with no possibility (to my knowledge) to move back to previous position.

 public class OneOfDeserializer
        : INodeDeserializer
    {

        public OneOfDeserializer(INodeDeserializer inner)
        {
            this.Inner = inner;
        }

        protected INodeDeserializer Inner { get; }

        public virtual bool Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, out object value)
        {
            value = null;
            var oneOfType = expectedType.GetGenericType(typeof(OneOf<,>));
            if(oneOfType == null)
                return this.Inner.Deserialize(reader, expectedType, nestedObjectDeserializer, out value);
            var t1 = oneOfType.GetGenericArguments()[0];
            var t2 = oneOfType.GetGenericArguments()[1];
            try
            {
                value = nestedObjectDeserializer(reader, t1);
            }
            catch
            {
                value = nestedObjectDeserializer(reader, t2);
            }
            value = Activator.CreateInstance(oneOfType, new object[] { value });
            return true;
        }

    }

Thanks in advance for the help!

[EdwardCooke]

No its not. All of YamlDotNet is forward only and it would be a large undertaking to undo that.

I'm going to close this for now, if you have additional comments, re-open it and we can discuss.