AutoMapper: “Ignore the rest”?

Question

Is there a way to tell AutoMapper to ignore all of the properties except the ones which are mapped explicitly?

I have external DTO classes which are likely to change from the outside and I want to avoid specifying each property to be ignored explicitly, since adding new properties will break the functionality (cause exceptions) when trying to map them into my own objects.

Answer 1

As of AutoMapper 5.0, the .TypeMap property on IMappingExpression is gone, meaning the 4.2 solution no longer works. I've created a solution which uses the original functionality but with a different syntax:

var config = new MapperConfiguration(cfg =>
{
    cfg.CreateMap<Src, Dest>();
    cfg.IgnoreUnmapped();        // Ignores unmapped properties on all maps
    cfg.IgnoreUnmapped<Src, Dest>();  // Ignores unmapped properties on specific map
});

// or add  inside a profile
public class MyProfile : Profile
{
   this.IgnoreUnmapped();
   CreateMap<MyType1, MyType2>();
}

Implementation:

public static class MapperExtensions
{
    private static void IgnoreUnmappedProperties(TypeMap map, IMappingExpression expr)
    {
        foreach (string propName in map.GetUnmappedPropertyNames())
        {
            if (map.SourceType.GetProperty(propName) != null)
            {
                expr.ForSourceMember(propName, opt => opt.Ignore());
            }
            if (map.DestinationType.GetProperty(propName) != null)
            {
                expr.ForMember(propName, opt => opt.Ignore());
            }
        }
    }

    public static void IgnoreUnmapped(this IProfileExpression profile)
    {
        profile.ForAllMaps(IgnoreUnmappedProperties);
    }

    public static void IgnoreUnmapped(this IProfileExpression profile, Func<TypeMap, bool> filter)
    {
        profile.ForAllMaps((map, expr) =>
        {
            if (filter(map))
            {
                IgnoreUnmappedProperties(map, expr);
            }
        });
    }

    public static void IgnoreUnmapped(this IProfileExpression profile, Type src, Type dest)
    {
        profile.IgnoreUnmapped((TypeMap map) => map.SourceType == src && map.DestinationType == dest);
    }

    public static void IgnoreUnmapped<TSrc, TDest>(this IProfileExpression profile)
    {
        profile.IgnoreUnmapped(typeof(TSrc), typeof(TDest));
    }
}

Answer 2

For those who are using the non-static API in version 4.2.0 and above, the following extension method (found here in the AutoMapperExtensions class) can be used:

// from http://stackoverflow.com/questions/954480/automapper-ignore-the-rest/6474397#6474397
public static IMappingExpression IgnoreAllNonExisting(this IMappingExpression expression)
{
    foreach(var property in expression.TypeMap.GetUnmappedPropertyNames())
    {
        expression.ForMember(property, opt => opt.Ignore());
    }
    return expression;
}

The important thing here is that once the static API is removed, code such as Mapper.FindTypeMapFor will no longer work, hence the use of the expression.TypeMap field.

Answer 3

For Automapper 5.0 in order to skip all unmapped properties you just need put

.ForAllOtherMembers(x=>x.Ignore());

at the end of your profile.

For example:

internal class AccountInfoEntityToAccountDtoProfile : Profile
{
    public AccountInfoEntityToAccountDtoProfile()
    {
        CreateMap<AccountInfoEntity, AccountDto>()
           .ForMember(d => d.Id, e => e.MapFrom(s => s.BankAcctInfo.BankAcctFrom.AcctId))
           .ForAllOtherMembers(x=>x.Ignore());
    }
}

In this case only Id field for output object will be resolved all other will be skipped. Works like a charm, seems we don't need any tricky extensions anymore!

Answer 4

You can use ForAllMembers, than overwrite only needed like this

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

Be carefull, it will ignore all, and if you will not add custom mapping, they are already ignore and will not work

also, i want to say, if you have unit test for AutoMapper. And you test that all models with all properties mapped correctly you shouldn't use such extension method

you should write ignore's explicitly

Answer 5

I've updated Can Gencer's extension to not overwrite any existing maps.

public static IMappingExpression<TSource, TDestination> 
    IgnoreAllNonExisting<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
{
    var sourceType = typeof (TSource);
    var destinationType = typeof (TDestination);
    var existingMaps = Mapper.GetAllTypeMaps().First(x => x.SourceType.Equals(sourceType) && x.DestinationType.Equals(destinationType));
    foreach (var property in existingMaps.GetUnmappedPropertyNames())
    {
        expression.ForMember(property, opt => opt.Ignore());
    }
    return expression;
}

Usage:

Mapper.CreateMap<SourceType, DestinationType>()
                .ForMember(prop => x.Property, opt => opt.MapFrom(src => src.OtherProperty))
                .IgnoreAllNonExisting();

Answer 6

This is an extension method I wrote that ignores all non existing properties on the destination. Not sure if it will still be useful as the question is more than two years old, but I ran into the same issue having to add a lot of manual Ignore calls.

public static IMappingExpression<TSource, TDestination> IgnoreAllNonExisting<TSource, TDestination>
(this IMappingExpression<TSource, TDestination> expression)
{
    var flags = BindingFlags.Public | BindingFlags.Instance;
    var sourceType = typeof (TSource);
    var destinationProperties = typeof (TDestination).GetProperties(flags);

    foreach (var property in destinationProperties)
    {
        if (sourceType.GetProperty(property.Name, flags) == null)
        {
            expression.ForMember(property.Name, opt => opt.Ignore());
        }
    }
    return expression;
}

Usage:

Mapper.CreateMap<SourceType, DestinationType>()
                .IgnoreAllNonExisting();

UPDATE: Apparently this does not work correctly if you have custom mappings because it overwrites them. I guess it could still work if call IgnoreAllNonExisting first and then the custom mappings later.

schdr has a solution (as an answer to this question) which uses Mapper.GetAllTypeMaps() to find out which properties are unmapped and auto ignore them. Seems like a more robust solution to me.