Method MapperFor

Namespace

Mapperion

Assembly

Mapperion.dll

MapperFor<TSource, TDestination>(IMapper)

Settles the map for a pair once and hands back the function, for a loop that maps the same pair many times.

public static Func<TSource, TDestination> MapperFor<TSource, TDestination>(this IMapper mapper)

Parameters

mapper IMapper

The mapper to bind.

Returns

Func<TSource, TDestination>

A function mapping one TSource to a new TDestination.

Type Parameters

TSource

The source type.

TDestination

The destination type.

Remarks

mapper.Map<Order, OrderDto>(order) is a generic method reached through an interface, and the runtime works out its type arguments on every call. None of that work depends on the object being mapped, so in a loop it is the same answer found over and over. This asks for it once:

Func<Order, OrderDto> toDto = mapper.MapperFor<Order, OrderDto>();

foreach (Order order in orders)
{
    results.Add(toDto(order));
}

The result is an ordinary Func<T, TResult>, so it also goes straight into a Select. It maps exactly what Map<TSource, TDestination>(TSource) maps, and it is bound to the configuration it came from.

Hold it for as long as the loop, or as a field beside the mapper. Asking for one per call costs more than it saves, since the work it avoids is the work it does. For a single map, Map is the one to write, and where mapping is genuinely what a program spends its time on, the source generator beats all of this.

Exceptions

ArgumentNullException

mapper is null.