Automapper null string to empty

Question

When I try to map an object that has a null string property, the destination is also null. Is there a global settings I can turn on that says all null string should be mapped to empty?

Answer 1

Something like this should work:

public class NullStringConverter : ITypeConverter<string, string>
  {
    public string Convert(string source)
    {
      return source ?? string.Empty;
    }
  }

And in your configuration class:

public class AutoMapperConfiguration
{
    public static void Configure()
    {
        Mapper.CreateMap<string, string>().ConvertUsing<NullStringConverter>();

        Mapper.AddProfile(new SomeViewModelMapper());
        Mapper.AddProfile(new SomeOtherViewModelMapper());
        ...
    }
}

Answer 2

If you need a non-global setting, and want to do it per property:

Mapper.CreateMap<X, Y>()
.ForMember(
    dest => dest.FieldA,
    opt => opt.NullSubstitute(string.Empty)
);

Answer 3

Similar to David Wick's answer, you can also use ConvertUsing with a lambda expression, which eliminates the requirement for an additional class.

Mapper.CreateMap<string, string>().ConvertUsing(s => s ?? string.Empty);