AutoMapper Map If Not Null, Otherwise Custom Conve

问题:

Here's my code:

Mapper.CreateMap<Foo, Foo2>()
   .ForMember(dest => dest.Bar, opt => opt.MapFrom(src => src.Bar == null ? new BarViewModel() : src.Bar))

Basically, "BarViewModel" has a parameterless ctor which sets up properties in the class.

So i'm trying to say to AutoMapper:

If the value is null, then use the ctor for the class. otherwise use the mapping you have in place

The above is giving me a C# compiler error. And i'm guessing a cast wouldn't work either.

So is there a AutoMapper trick to do this?

Worst case i could remove that mapping for that property, and just do:

var mapped = Mapper.Map<Foo,Foo2>(src);
if (mapped.Bar == null) mapped.Bar = new BarViewModel();

But that's a tad ugly.

Ideas?

回答1:

You can use custom value resolver. The following should work:

Mapper.CreateMap<Foo, Foo2>()
   .ForMember(dest => dest.Bar, opt => opt.ResolveUsing(src => src.Bar == null ? new Bar() : Mapper.Map<Bar,Bar2>(src.Bar)))

回答2:

Now you can use .NullSubstitute() to replace NULL value to some custom value in Automapper, e.g.:

CreateMap<SMModel, VM_SMModel>()
                    .ForMember(d => d.myDate, o => o.NullSubstitute(new DateTime(2017,12,12)));

回答3:

I don't get a compiler error for the following:

public class Foo
{
    public Bar Bar { get; set; }
}

public class Foo2
{
    public Bar Bar { get; set; }
}

public class Bar
{
    public int Id { get; set; }

    public Bar()
    {
        Id = 3;
    }
}

CreateMap<Foo, Foo2>()
    .ForMember(
        dest => dest.Bar,
        opt => opt.MapFrom(src => src.Bar == null ? new Bar() : src.Bar));

...so I'm wondering if the problem is not actually with your mapping?

回答4:

As of Automapper 8, ResolveUsing is no longer an option but inline Func's, IValueResolver and IMemberValueResolver are