Flattening and unflattening
It is pretty common to flatten objects during mapping, eg. Car.Make.Id => CarDto.MakeId.
Mapperly tries to figure out flattenings automatically by making use of the pascal case C# notation.
If Mapperly can't resolve the target or source property correctly, it is possible to manually configure it by applying the MapPropertyAttribute
by either using the source and target property path names as arrays or using a dot separated property access path string
[MapProperty([nameof(Car.Make), nameof(Car.Make.Id)], [nameof(CarDto.MakeId)])]
// Or alternatively
[MapProperty("Make.Id", "MakeId")]
// Or
[MapProperty($"{nameof(Make)}.{nameof(Make.Id)}", "MakeId")]
partial CarDto Map(Car car);
Unflattening is not automatically configured by Mapperly and needs to be configured manually via MapPropertyAttribute.
Flatten all members of property
If a property has many members that need to be flattened but that cannot be figured out automatically, this can be configured using the MapNestedProperties attribute.
This will bring all sub-members of a specified member into scope as if they were defined on the source object:
[MapProperty([nameof(Car.Engine), nameof(Car.Engine.Horsepower)], [nameof(CarDto.Horsepower)])]
[MapProperty([nameof(Car.Engine), nameof(Car.Engine.FuelType)], [nameof(CarDto.FuelType)])]
[MapProperty([nameof(Car.Engine), nameof(Car.Engine.Cylinders)], [nameof(CarDto.Cylinders)])]
// Is equivalent to:
[MapNestedProperties(nameof(Car.Engine))]
partial CarDto Map(Car car);
The nested members have a lower priority than all immediate members of the source object.
E.g. if both the Car and the Engine classes in the preceding example contained an Id property, the CarDto.Id property would be mapped from Car.Id.
Similarly, the automatic flattening has precedence over the nested members:
CarDto.EngineId would be mapped from Car.Engine.Id rather than Car.Engine.EngineId if Engine contained both.
If multiple MapNestedProperties are defined that contain members that match to the same member on the target object, no guarantees are made as to which source member is chosen.
In such a case it is therefore recommended to define the expected property mapping explicitly using a MapProperty attribute.
Experimental full nameof
Mapperly supports an experimental "fullnameof".
It can be used to configure property paths using nameof.
Opt-in is done by prefixing the path with @.
[MapProperty(nameof(@Car.Make.Id), nameof(CarDto.MakeId))]
partial CarDto Map(Car car);
@nameof(Car.Make.Id) will result in the property path Make.Id.
The first part of the property path is stripped.
Make sure these property paths start with the type of the property and not with a namespace or a property.
This is an experimental API. Its API surface is not subject to semantic releases and may break in any release.