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IQueryable projections

Mapperly does support IQueryable<T> projections:

[Mapper]
public static partial class CarMapper
{
    public static partial IQueryable<CarDto> ProjectToDto(this IQueryable<Car> q);
}

This is useful in combination with Entity Framework and other ORM solutions which expose IQueryable<T>. Only fields present in the target class will be retrieved from the database.

info

Since queryable projection mappings use System.Linq.Expressions.Expression<T> under the hood, such mappings have several limitations:

  • Object factories are not applied
  • Constructors with unmatched optional parameters are ignored
  • ThrowOnPropertyMappingNullMismatch is ignored
  • AllowNullPropertyAssignment is ignored
  • Enum mappings do not support the ByName strategy
  • Reference handling is not supported
  • Nullable reference types are disabled
  • User implemented mapping methods need to follow expression tree limitations.

Property configurations​

To configure property mappings add partial mapping method definitions with attributes as needed. Set these methods to private to hide them from callers.

[Mapper]
public static partial class CarMapper
{
    public static partial IQueryable<CarDto> ProjectToDto(this IQueryable<Car> q);

    [MapProperty(nameof(Car.Manufacturer), nameof(CarDto.Producer)]
    private static partial CarDto Map(Car car);
}