Using AutoMapper to merge objects

Question

I\'m attempting to use AutoMapper to merge data from multiple objects, and I\'m running into a couple issues that I can\'t seem to solve.

I have an object like:

Answer 1

Automapper is capable of this, your mapper needs to be configured as such:

Mapper.Initialize(cfg =>
{
    // necessary if you are mapping parent to a parent
    cfg.CreateMap<Parent, Parent>()
        .ForAllMembers(options =>
        {
            options.Condition(src => src.DestinationValue == null);
        });
    // necessary if you are mapping your child to a child
    cfg.CreateMap<Child, Child>()
        .ForAllMembers(options =>
        {
            options.Condition(src => src.DestinationValue == null);
        });
});

And then your usage as such:

var bigParent = new Parent
{
    Id = "14",
    Children = new List<Child>
    {
        new Child
        {
            Key = "A",
            Value1 = 10,
            Value2 = 20,
            Value3 = 30,
            Value4 = 40,
            Value5 = 50
        }
    }
};

var merge = new Parent
{
    Id = "14",
    Children = new List<Child>
    {
        new Child
        {
            Key = "A",
            Value1 = null,
            Value2 = null,
            Value3 = 100,
            Value4 = null,
            Value5 = null
        }
    }
};

var bigChild = new Child
{
    Key = "A",
    Value1 = 10,
    Value2 = 20,
    Value3 = 30,
    Value4 = 40,
    Value5 = 50
};

var mergeChild = new Child
{
    Key = "A",
    Value1 = null,
    Value2 = null,
    Value3 = 100,
    Value4 = null,
    Value5 = null
};

Mapper.Map(bigChild, mergeChild);
Debug.Assert(mergeChild.Value3 == 100);

Mapper.Map(bigParent, merge);
Debug.Assert(merge.Children[0].Value3 == 100);

Answer 2

If you want to ignore null values in mappings defined in AutoMapper Profile, use:

public class MappingProfile : AutoMapper.Profile
{
  public MappingProfile()
  {
     this.CreateMap<Parent, Parent>()
         .ForAllMembers(o => o.Condition((source, destination, member) => member != null));
  }
}