c# - Automapper: mapping collection and passing parameter

Question

I am trying to map one entity to another (which has one additional field).

Group {
    int Id;
}

GroupExtended {
   int Id;
   string Description;
}

So I do the mapping in loop:

foreach (var group in groups)
{
     var result = mapper.Map<Group, GroupExtended>(group,
                        opt => opt.AfterMap((src, dest) => dest.Description = someValue));
}

Is that possible to map entire IEnumerable, and still passing an the value ? I tried this:

var result = mapper.Map<List<GroupExtended>>(groups,
                        opt => opt.AfterMap((src, dest) => dest.Description = someValue));

But it has an error on dest.Description : 'object' does not contain definition of "Description"

Answer 1

Yes, it is possible to map an entire collection and still pass the value. Using a custom value resolver is probably the preferred option, as pointed out in the comment on your original post. If you'd still prefer to use AfterMap, you can do something like the following, remembering that your source and destination in this case are collections rather than individual items:

var result = mapper.Map<List<Group>, List<GroupExtended>>(groups,
    opt => opt.AfterMap((src, dest) =>
    {
        foreach (var i in dest)
        {
            i.Description = "someValue";
        }
    }));