So, here's a quick object structure that I have.

[
    {
        id
        ...
        ...
        children: [
            {
                id
                ...
                ...
                children: [
                    {
                        id
                        ...
                        ...
                        finalChild: {
                            id
                            ...
                            ...
                            someDecimal: xxx
                        }
                    }
                    ...
                    ...
                    ...
                ]
            }
            ...
            ...
            ...
        }
    }
    ...
    ...
    ...
]

I can get all of that through LINQ and Entity Framework no problem. Now, I need to flatten all of that for a new DTO I'm creating that will roll that someDecimal all the way up to the top and SUM it for all children down the line. I know I can use the SUM LINQ function, but it causes some errors. Mainly because...finalChild could, potentially, be null. In addition, the lambda expression that I'm trying to build warns me that it would bind it 300 times to do so.

Is there a better way to do this? Maybe I should be doing it outside of an Automapper?

Here's the line of code that's giving me trouble:

.ForMember(dest => dest.RollUpSum, 
           src => src.MapFrom(x => x.children.Sum(x => x.children.finalChild.Sum(x => x.someDecimal))));