如何忽略所有目标成员，除了映射的成员？

Try to use .ConvertUsing() in your case, e.g.

CreateMap<Source,Target>()
.ConvertUsing(converter=> new Target(){
P1 = converter.P1,
....
});

So, you can describe all properties what you want to have in your object, other will be ignored.

I struggled with this one for quite a while too, or at least a problem similar to this. I had a class with a lot of properties on it (about 30) and I only wanted to map about 4 of them. It seems crazy to add 26 ignore statements (especially when it means that future changes to the class will mean having to update them!)

I finally found that I could tell AutoMapper to ignore everything, and then explicitly add the ones that I did want.

// Create a map, store a reference to it in a local variable
var map = CreateMap<Source,Target>();


// Ignore all members
map.ForAllMembers(opt => opt.Ignore());


// Add mapping for P1
map.ForMember(dest => dest.P1, opt => opt.MapFrom( src => src.P1));


// Add other mappings...
map.ForMember(dest => dest.P2, opt => opt.MapFrom( src => src.P2));
map.ForMember(dest => dest.P3, opt => opt.MapFrom( src => src.P3));
map.ForMember(dest => dest.P4, opt => opt.MapFrom( src => src.P4));

You'd be forgiven for thinking that you could just do this (but don't because it wont compile):

// This won't compile
CreateMap<Source,Target>()
.ForAllMembers(opt => opt.Ignore())
.ForMember(dest => dest.P1, opt => opt.MapFrom( src => src.P1));

The reason why this doesn't work is that the ForAllMembers() method doesn't support the fluent style of chaining (at least in the current version 2.0).

The good news is that the non-chaining version does indeed work. The one caveat of course is that you need to explicitly tell AutoMapper which members to map. I haven't yet found an easy way to have it both ways so that you can still use the implied mappings and ignore the broken ones.

This is working for me:

public static class MappingExpressionExtensions
{
public static IMappingExpression<TSource, TDest> IgnoreAllUnmapped<TSource, TDest>(this IMappingExpression<TSource, TDest> expression)
{
expression.ForAllMembers(opt => opt.Ignore());
return expression;
}
}

Because ForAllMembers returns void, calling ForAllMembers(o => o.Ignore()) without this extension method wouldn't work. We want to keep the mapping expression available to enable the subsequent mappings:

CreateMap<Source, Destination>()
.IgnoreAllUnmapped()
.ForMember(d => d.Text, o => o.MapFrom(s => s.Name))
.ForMember(d => d.Value, o => o.MapFrom(s => s.Id));

To avoid having to explicitly specify the mapped properties, you can use IgnoreAllNonExisting. It ignores any destination properties that don't have mapped source properties.

Extension method which allows fluent syntax for the ForAllMembers method:

public static IMappingExpression<TSource, TDestination> IgnoreAllMembers<TSource, TDestination>(
this IMappingExpression<TSource, TDestination> expression
)
{
expression.ForAllMembers(opt => opt.Ignore());
return expression;
}

Usage:

The call to IgnoreAllMembers must be before the call to ForMember.

        CreateMap<LocationRevision, Dto.LocationAddressMap>()
.IgnoreAllMembers()
.ForMember(m => m.LocationId, opt => opt.MapFrom(src => src.Id))
;