How to configure Conditional Mapping in AutoMapper?

Question

Suppose I have the following entities (classes)

public class Target
{
    public string Value;
}


public class Source
{
    public string Value1;
    public string Value2;
}

Now I want to configure Auto Map, to Map Value1 to Value if Value1 starts with "A", but otherwise I want to map Value2 to Value.

This is what I have so far:

Mapper
    .CreateMap<Source,Target>()
    .ForMember(t => t.Value, 
        o => 
            {
                o.Condition(s => 
                    s.Value1.StartsWith("A"));
                o.MapFrom(s => s.Value1);
                  <<***But then how do I supply the negative clause!?***>>
            })

However the part the still eludes me is how to tell AutoMapper to go take s.Value2 should the earlier condition fails.

It just seems to me the API was not designed as well as it could be... but may be it's my lack of knowledge getting in the way.

Olsen

Just have a second ForMember call with the inverse of the condition in this one if you're really stuck and the answer provided by Tejal doesn't cut it. – Pelton

Answer 1

Try this

 Mapper.CreateMap<Source, Target>()
        .ForMember(dest => dest.Value, 
                   opt => opt.MapFrom
                   (src => src.Value1.StartsWith("A") ? src.Value1 : src.Value2));

Condition option is used to add conditions to properties that must be met before that property will be mapped and MapFrom option is used to perform custom source/destination member mappings.

Hermitage

Hmmm I actually need a way to access the target value too somehow - but still this answers the question asked. – Olsen

What are you exactly trying to do? – Hermitage

The condition is a bit more complex than the one described, that depends on the source value only. I need to somehow get to the resolutioncontext and figure out the target value as well. – Olsen

Answer 2

AutoMapper allows adding conditions to properties that must be met before that property will be mapped.

Mapper.CreateMap<Source,Target>()
      .ForMember(t => t.Value, opt => 
            {
                opt.PreCondition(s => s.Value1.StartsWith("A"));
                opt.MapFrom(s => s.Value1);
            })

Heger

Hi and welcome to stackoverflow, and thank you for answering. While this code might answer the question, can you consider adding some explanation for what the problem was you solved, and how you solved it? This will help future readers to understand your answer better and learn from it. – Kentonkentucky

the best way is this answer – Chignon

Except it doesn't work if you're using ProjectTo – Calcutta

Answer 3

With the conditional mapping you only can configure when the mapping should executed for the specified destination property.

So it means you can't define two mappings with different conditions for the same destination property.

If you have a condition like "if condition is true then use PropertyA else use PropertyB" then you should do it like "Tejal" wrote:

opt.MapFrom(src => src.Value1.StartsWith("A") ? src.Value1 : src.Value2)

Kwan

Answer 4

AutoMapper allows you to add conditions to properties that must be met before that property will be mapped.

I was doing the mapping with some enum conditions, have a look that is little effort for the community from my side.

}

.ForMember(dest => dest.CurrentOrientationName, 
             opts => opts.MapFrom(src => src.IsLandscape? 
                                        PageSetupEditorOrientationViewModel.Orientation.Landscape : 
                                        PageSetupEditorOrientationViewModel.Orientation.Portrait));

Niacin