Mapping readonly child collection with AutoMapper

Question

It\'s not so much a question, as I have found a way to do what I want, but it seems like there should be a better way to do it. I\'ve searched everywhere and not found anything.

Answer 1

I don't like to have logic inside property getter or setter, but what about adding setter to Children property of Parent class

public class Parent
{
    private readonly IList<Child> _children = new List<Child>();

    public IEnumerable<Child> Children
    {
        get => _children;
        set => AddChildren(value);
    }

    public void AddChild(Child child)
    {
        child.Parent = this;
        _children.Add(child);
    }

    private void AddChildren(IEnumerable<Child> children)
    {
        _children.Clear();

        foreach (var child in children)
        {
            AddChild(child);
        }
    }
}

And AfterMap logic is not more necessary. Mapping configuration will be simple

Mapper.CreateMap<ParentDTO, Parent>();

Answer 2

I think if you are going to protect properties for good business logic reasons then it would be bad if AutoMapper circumvented them when doing its mapping. In situations like this I prefer to abandon the fluent syntax and place the creation logic in its own method like this:

private Parent MapParentDTOToParent(ParentDTO source)
{
    var parent = new Parent();
    // Business logic here
    return parent
}

and then:

Mapper.CreateMap<ParentDTO, Parent>().ConvertUsing(MapParentDTOToParent);

I find this easier to follow than having lots of ignore declarations.