How to configure Conditional Mapping in AutoMapper?

问题

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.

回答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.

回答2:

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)

回答3:

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));

来源：https://stackoverflow.com/questions/17822882/how-to-configure-conditional-mapping-in-automapper

标签

lambda

automapper

automapper-2