Ignore mapping one property with Automapper

Question

I'm using Automapper and I have the following scenario: Class OrderModel has a property called 'ProductName' that isn't in the database. So when I try to do the mapping with:

Mapper.CreateMap<OrderModel, Orders>(); 

It generates an exception :

"The following 1 properties on Project.ViewModels.OrderModel are not mapped: 'ProductName'

I've read at AutoMapper's Wiki for Projections the opposite case (the extra attribute is on the destination, not in the source which is actually my case )

How can I avoid automapper to make the mapping of this property?

Answer 1

I'm perhaps a bit of a perfectionist; I don't really like the ForMember(..., x => x.Ignore()) syntax. It's a little thing, but it it matters to me. I wrote this extension method to make it a bit nicer:

public static IMappingExpression<TSource, TDestination> Ignore<TSource, TDestination>(
    this IMappingExpression<TSource, TDestination> map,
    Expression<Func<TDestination, object>> selector)
{
    map.ForMember(selector, config => config.Ignore());
    return map;
}

It can be used like so:

Mapper.CreateMap<JsonRecord, DatabaseRecord>()
        .Ignore(record => record.Field)
        .Ignore(record => record.AnotherField)
        .Ignore(record => record.Etc);

You could also rewrite it to work with params, but I don't like the look of a method with loads of lambdas.

Answer 2

When mapping a view model back to a domain model, it can be much cleaner to simply validate the source member list rather than the destination member list

Mapper.CreateMap<OrderModel, Orders>(MemberList.Source); 

Now my mapping validation doesn't fail, requiring another Ignore(), every time I add a property to my domain class.