Interfaces

Maps can map/match/project types based on certain conditions of the context, to achieve this you can implement the corresponding optional interfaces for your maps:

• ICanMapNew<TSource, TDestination> for INewMap<TSource, TDestination>
• ICanMapMerge<TSource, TDestination> for IMergeMap<TSource, TDestination>
• ICanMatch<TSource, TDestination> for IMatchMap<TSource, TDestination>
• ICanMatchHierarchy<TSource, TDestination> for IHierarchyMatchMap<TSource, TDestination>
• ICanProject<TSource, TDestination> for IProjectionMap<TSource, TDestination>
• ICanMapAsyncNew<TSource, TDestination> for IAsyncNewMap<TSource, TDestination>
• ICanMapAsyncMerge<TSource, TDestination> for IAsyncMergeMap<TSource, TDestination>

If you are on .NET 7 or greater you can use the static versions of the interfaces above instead:

• ICanMapNewStatic<TSource, TDestination>
• ICanMapMergeStatic<TSource, TDestination>
• ICanMatchStatic<TSource, TDestination>
• ICanMatchHierarchyStatic<TSource, TDestination>
• ICanProjectStatic<TSource, TDestination>
• ICanMapAsyncNewStatic<TSource, TDestination>
• ICanMapAsyncMergeStatic<TSource, TDestination>

This allows you to check condition before invoking your maps, if you return false your map will be ignored, and depending on the mapper another map/mapper may be executed or the mapper might throw MapNotFoundException.

Maps themselves cannot throw MapNotFoundException to map conditionally, for performance reasons. All the exceptions thrown inside the maps will be wrapped in MappingException/MatcherException/ProjectionException (except OperationCanceledException to allow CancellationToken cancellation propagation).

public class MyMaps :
	ICanMapNew<Product, ProductDto>,
	INewMap<Product, ProductDto>
{
	public bool CanMapNew(MappingContext context){
		// Prevent the map from being used by a CollectionMapper because
		// it might be inefficient to do so (simplified check)
		return context.MappingOptions.GetOptions<NestedMappingContext>()?.ParentMapper is not CollectionMapper;
	}

	public ProductDto? Map(Product? source, MappingContext context){
		if(source == null)
			return null;
		else{
			return new ProductDto{
				Code = source.Code,
				...
			};
		}
	}
}

Additional maps

Conditional mapping is also available for additional maps, simply use the overload which accepts two methods:

var additionalNewMaps = new CustomNewAdditionalMapsOptions();
additionalNewMaps.AddMap<Product, ProductDto>(
	(s, c) => ...,
	c => c.MappingOptions.GetOptions<NestedMappingContext>()?.ParentMapper is not CollectionMapper);