AutoMapper set destination to null on condition of source property

问题

I'm mapping between two objects and based on a condition of the source I would like the destination to be null.

For example, here are the classes:

public class Foo
{
    public int Code { get; set; }
    public string Name { get; set; }

}

public class Bar
{
    public string Name { get; set; }
    public string Type { get; set; }
}

And my map:

Mapper.CreateMap<Foo, Bar>()
            .AfterMap((s, d) => { if (s.Code != 0) d = null; });

But it seems to ignore the AfterMap. Bar is initialised although with all default properties.

How can I get the mapper to return null based on Code not being equal to 0?

Thanks

回答1:

One possible way is -

class Converter : TypeConverter<Foo, Bar>
{
    protected override Bar ConvertCore(Foo source)
    {
        if (source.Code != 0)
            return null;
        return new Bar();
    }
}


static void Main(string[] args)
    {
        Mapper.CreateMap<Foo, Bar>()
            .ConvertUsing<Converter>();


        var bar = Mapper.Map<Bar>(new Foo
        {
            Code = 1
        });
        //bar == null true
    }

回答2:

I created the following extension method to solve this problem.

public static IMappingExpression<TSource, TDestination> PreCondition<TSource, TDestination>(
   this IMappingExpression<TSource, TDestination> mapping
 , Func<TSource, bool> condition
)
   where TDestination : new()
{
   // This will configure the mapping to return null if the source object condition fails
   mapping.ConstructUsing(
      src => condition(src)
         ? new TDestination()
         : default(TDestination)
   );

   // This will configure the mapping to ignore all member mappings to the null destination object
   mapping.ForAllMembers(opt => opt.PreCondition(condition));

   return mapping;
}

For the case in question, it can be used like this:

Mapper.CreateMap<Foo, Bar>()
      .PreCondition(src => src.Code == 0);

Now, if the condition fails, the mapper will return null; otherwise, it will return the mapped object.

来源：https://stackoverflow.com/questions/34288574/automapper-set-destination-to-null-on-condition-of-source-property

标签

automapper