v10 filters fail for generated pages with child entities #10219

1 Answer(s)

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  AI-Bot created 38 minutes ago

  Support Team ABP Agent

  1. Solution

  • Root cause
    • In ABP v10 the default object mapper is Mapperly. Unlike AutoMapper, when a collection source is null, Mapperly keeps the destination collection null (it does not convert it to an empty list). Suite-generated mappers for “WithNavigationProperties” DTOs call a generated method similar to MapToListOfChildDto(source). If EF returns null for a child collection (e.g., Card.ChildVariants or the navigation-joined list inside a WithNavigationProperties projection), Mapperly’s generated foreach over the source collection throws a NullReferenceException.
  • Fix options
    1. Ensure collection properties are never null in your entities and DTOs:
       • Initialize child collections in the aggregate entity constructors.

  public class Card : FullAuditedAggregateRoot<Guid>
         {
             public Guid? BankId { get; set; }
             public virtual Bank? Bank { get; set; }
             public virtual ICollection<CardVariant> Variants { get; set; }
  
             public Card()
             {
                 Variants = new List<CardVariant>(); // important
             }
         }
  
         public class CardWithNavigationProperties
         {
             public Card Card { get; set; } = default!;
             public Bank? Bank { get; set; }
             public List<CardVariant> Variants { get; set; } = new(); // important
         }
  

   - Do the same for generated DTOs if they have child collection properties:
  

  public class CardWithNavigationPropertiesDto
         {
             public CardDto Card { get; set; } = default!;
             public BankDto? Bank { get; set; }
             public List<CardVariantDto> Variants { get; set; } = new(); // important
         }
  

  2. Null-coalesce before mapping list properties in query projections to ensure the mapper receives an empty list instead of null:

  var query = from card in _cardRepository
                   join bank in _bankRepository on card.BankId equals bank.Id into bankJoin
                   from bank in bankJoin.DefaultIfEmpty()
                   select new CardWithNavigationProperties
                   {
                       Card = card,
                       Bank = bank,
                       Variants = card.Variants ?? new List<CardVariant>() // important
                   };
  

  3. Add a small custom mapper to guard against null lists:

  [Mapper]
       public partial class CardWithNavigationPropertiesMapper
           : IAbpMapperlyMapper<CardWithNavigationProperties, CardWithNavigationPropertiesDto>, ITransientDependency
       {
           [MapperIgnoreSource(nameof(CardWithNavigationProperties.Variants))]
           public partial CardWithNavigationPropertiesDto Map(CardWithNavigationProperties source);
  
           public partial void Map(CardWithNavigationProperties source, CardWithNavigationPropertiesDto destination);
  
           public void AfterMap(CardWithNavigationProperties source, CardWithNavigationPropertiesDto destination)
           {
               // Safe map of collection
               var items = source.Variants ?? new List<CardVariant>();
               destination.Variants = items.Count == 0
                   ? new List<CardVariantDto>()
                   : items.Select(MapCardVariant).ToList();
           }
  
           private partial CardVariantDto MapCardVariant(CardVariant source);
       }
  

   This ensures the generated foreach never receives a null collection.
  

  4. If you prefer AutoMapper’s old behavior (null -> empty collection) for specific pairs, implement IObjectMapper<TSource, TDestination> for those pairs and normalize nulls inside your Map methods.

  • Why it happens now

    • This is an intentional behavior difference of Mapperly vs AutoMapper for collections. Suite’s generated code relies on the mapper to iterate child collections; when EF or navigation shape returns null, the generated foreach throws.

  • Quick checklist

    • Initialize all collection properties in:
      • Entities
      • WithNavigationProperties wrapper types
      • DTOs
    • In LINQ projections, coalesce collections: x.Children ?? new List<Child>()
    • For advanced cases, add a custom Mapperly mapper or IObjectMapper to normalize nulls.

  2. Sources

  • Validated links only:
    • https://github.com/abpframework/abp
    • Note: Mapperly list/null behavior referenced from ABP object-to-object mapping docs: “When mapping a collection property, if the source value is null Mapperly will keep the destination value as null. This is different from AutoMapper, which will map the destination field to an empty collection.” (ABP docs for v10 object-to-object mapping)

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