How to add AutoMapper.Collection in ABP Framework

1. Install the needed NuGet packages

PM> Install-Package AutoMapper.Collection

2. Call AddCollectionMappers() in your AbpModule class

[DependsOn(typeof(AbpAutoMapperModule))]
public class MyModule : AbpModule
{
    public override void ConfigureServices(ServiceConfigurationContext context)
    {
        Configure<AbpAutoMapperOptions>(options =>
        {
            options.Configurators.Add(context =>
            {
                context.MapperConfiguration.AddCollectionMappers();
            });
            options.AddMaps<MyModule>();
        });
    }
}

3. Use EqualityComparison() in your AutoMapper.Profile class

public class AutoMapperProfile : Profile
{
    public AutoMapperProfile()
    {
        ...        
        CreateMap<OrderDTO, Order>();

        CreateMap<OrderItemDTO, OrderItem>()
          .EqualityComparison((odto, o) => odto.ID == o.ID);
        ...
    }
}

Please see the AutoMapper.Collection docs for the explanation of what EqualityComparison() does.

Demo

I created a demo for this using the Todo App from the abp-samples repository.

Go here to view the demo.

Or clone my fork of the abp-samples repository, then checkout branch play/AutoMapper.Collection

> git clone https://github.com/jflaga/abp-samples.git
> git checkout play/AutoMapper.Collection

The code which uses AutoMapper.Collection in there is the “Update Todo Item” appservice.

To test this yourself, check the integration tests for updating a Todo item located in /TodoApp.Application.Tests/Todo/UpdateTodoItemTests.cs.

AutoMapper.Collection does not work with IReadOnlyCollection or IEnumerable

While working on the demo project, I learned that AutoMapper.Collection does not work with IReadOnlyCollection or IEnumerable.

It throws this error message when I use those collection classes:

System.AggregateException : One or more errors occurred. (The instance of entity type 'TodoSubItem' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.

One solution is to use ICollection instead.

But if you need to use IReadOnlyCollection, a solution to the said error can be found here, which I also implemented in the demo project I mentioned above.