Argument exception: Source and destination must have same number of arguments

[Mytza]

Hi,

I am upgrading from an old version of automapper (4.2.1) to latest. We had expression mapping in place between DTO and entities. I am now getting this exception when trying to map an expression from a dto that has extra collection properties that are not present on the entity.
This was working before upgrade.

Is it possible to handle this scenario like it was before. I looked over the source code and could not find any way to configure this.

Thanks in advance,
Mihai

[BlaiseD]

It's easier to help with a failing sample. Please include the smallest possible sample reproducing the error here, or as a gist or here.

[Mytza]

Hi,

I have tried to make a new project and recreate the situation with a smaller number of mappings, and the expression mapping works even if i have an extra collection property on DTO.
In my solution I am facing problems only with a single expression map concerning DTO to entity, the rest are working.

Maybe you can give me some hints what to look at, i am not sure what is causing the problem.

Regards,
Mihai

[BlaiseD]

We'll need to see the expression to be helpful. I would look at some of the test cases as examples. Show the source and destination objects with an expression reproducing the problem.

[artemvalmus]

Hi.

I faced the same issue. Please take a look at the example below:

References:

<PackageReference Include="AutoMapper" Version="7.0.1" />
<PackageReference Include="AutoMapper.Extensions.ExpressionMapping" Version="1.0.2" />

Console app:

namespace ConsoleApp
{
    class Program
    {
        class OrderModel
        {
            public IEnumerable<ItemModel> Items { get; set; }
        }

        class ItemModel
        {
            public string Name { get; set; }
        }

        class OrderEntity
        {
            public OrderData OrderData { get; set; }
        }

        class OrderData
        {
            public IEnumerable<ItemEntity> Items { get; set; }
        }

        class ItemEntity
        {
            public string Name { get; set; }
        }

        static void Main(string[] args)
        {
            var config = new MapperConfiguration(cfg => {
                cfg.CreateMap<OrderEntity, OrderModel>()
                    .ForMember(x => x.Items, opt => opt.MapFrom(x => x.OrderData.Items));
                cfg.CreateMap<ItemEntity, ItemModel>();

                cfg.AddExpressionMapping();
            });

            var mapper = config.CreateMapper();

            Expression<Func<OrderModel, bool>> src = x => x.Items.Any(i => i.Name == "Test");

            // exception: Source and destination must have the same number of arguments
            var dest = mapper.Map<Expression<Func<OrderEntity, bool>>>(src);

            Console.ReadKey();
        }
    }
}

[BlaiseD]

OK the bug is here.

Fix:

    if (pm.SourceMembers == null || pm.SourceMembers.Count() == 0)
        continue;

I'll open a PR. Thanks guys.