CODEWITHSUNDEEP
c#.netautomapper
Andrew Savinykh
Andrew Savinykh

Reputation: 26290

Is it possible to map to null when a property on source is false?

I'm defining a mapping between a source class and a target class:

Mapper.CreateMap<Source, Target>();

I want the mapping to return null if a certain property on the Source is set to a particular value:

// If Source.IsValid = false I want the mapping to return null
Source s = new Source { IsValid = false };
Target t = Mapper.Map<Target>(s);
Assert.IsNull(t);

How do I configure AutoMapper to achieve that?

Upvotes: 3

Views: 4072

Answers (2)

Andrew Savinykh
Andrew Savinykh

Reputation: 26290

You can define your mapping like this:

Mapper.CreateMap<Source, Target>().TypeMap
  .SetCondition(r => ((Source)r.SourceValue).IsValid);

Upvotes: 3

samy
samy

Reputation: 14962

EDIT

If you want your map to output a null object I'd recommend using two levels of mapping: the first level decides whether or not to return a null object by taking over mapping behavior with the ConvertUsing method, and if mapping is required it defers it to an inner mapping engine:

static void Main(string[] args)
{
    var innerConfigurationStore = new ConfigurationStore(new TypeMapFactory(), MapperRegistry.Mappers);
    innerConfigurationStore.CreateMap<From, To>()
                .ForMember(to => to.DestinationName, opt => opt.MapFrom(from => from.Active ? from.Name : (string)null));
    var innerMappingEngine = new MappingEngine(innerConfigurationStore);

    Mapper.CreateMap<From, To>()
        .ConvertUsing(from => from.Active ? innerMappingEngine.Map<To>(from) : null)
        ;

    WriteMappedFrom(new From() {Active = true, Name = "ActiveFrom"});
    WriteMappedFrom(new From() {Active = false, Name = "InactiveFrom"});
}

static void WriteMappedFrom(From from)
{
    Console.WriteLine("Mapping from " + (from.Active ? "active" : "inactive") + " " + from.Name);
    var to = Mapper.Map<To>(from);
    Console.WriteLine("To -> " + (to == null ? "null" :  "not null"));
}

INITIAL ANSWER

It's quite simple to use a conditional mapping in Automapper, here is some sample code

public class From
{
    public bool Active { get; set; }
    public string Name { get; set; }
}

public class To
{
    public string DestinationName { get; set; }
}
static void Main(string[] args)
{
    Mapper.CreateMap<From, To>()
        .ForMember(to => to.DestinationName, opt => opt.MapFrom(from => from.Active ? from.Name : (string)null));

    WriteMappedFrom(new From() {Active = true, Name = "ActiveFrom"});
    WriteMappedFrom(new From() {Active = false, Name = "InactiveFrom"});
}

static void WriteMappedFrom(From from)
{
    Console.WriteLine("Mapping from " + (from.Active ? "active" : "inactive") + " " + from.Name);
    var to = Mapper.Map<To>(from);
    Console.WriteLine("To -> " + (to.DestinationName ?? "null"));
}

There are other conditional mappings in automapper but they seem to work only on convention-based mappings. You could however look into the documentation a bit more to confirm

Upvotes: 1

Related Questions