MapDynamic with array property always results in a single-member array

[FilipFilipov]

You can reproduce this easily in your MapDynamicTests if you change the Customer's Order type from ICollection<Order> to Order[] and then try to map a customer with more than one Order. The resulting array will always contain only the final Order.

Looking through the code I think this is caused by the MapCollection method, which for arrays does

var arrayList = new ArrayList { instanceToAddToCollectionInstance };

or in the case where isNewlyCreatedInstance is false

var arrayList = new ArrayList((ICollection)instance);

In both cases shouldn't that instead be

var arrayList = new ArrayList((ICollection)instance) { instanceToAddToCollectionInstance };

[Flaniga3]

@FilipFilipov Not sure if you're still struggling with this, but I ran into this same issue and no one anywhere could help. Finally I came up with this somewhat brutal solution in this stack overflow question: https://stackoverflow.com/questions/47239739/slapper-only-maps-one-object-when-selecting-multiple-objects-from-database. Check my first edit.

[FilipFilipov]

Oh, I just merged Slapper into my codebase and did the fix I suggested above myself. I'd make a pull request to upstream it, but this project is obviously not maintained anymore.

[Flaniga3]

@FilipFilipov I might consider taking that route myself. Thanks for posting your solution.

[odelvalle]

Hi @FilipFilipov I changed ICollection to array in Order, and this test pass without change anything in MapCollection:

[Test]
public void Can_Handle_Mapping_A_Single_Dynamic_Object_With_Multiple_Childs()
{
	// Arrange
	dynamic dynamicCustomer = new ExpandoObject();
	dynamicCustomer.Id = 1;
	dynamicCustomer.FirstName = "Bob";
	dynamicCustomer.LastName = "Smith";
	dynamicCustomer.Orders = new[]
	{
		new Order {Id = 1, OrderTotal = 50.50m},
		new Order {Id = 2, OrderTotal = 60.50m},
	};

	// Act
	var customer = Slapper.AutoMapper.MapDynamic<Customer>(dynamicCustomer) as Customer;

	// Assert
	Assert.NotNull(customer);
	Assert.That(customer.Orders.Count() == 2);
}

Can you send me any test that fail?
Thanks

[Flaniga3]

@odelvalle The StackOverflow link I posted outlines a very specific example of the mapper returning a single member IEnumerable when there should clearly be multiple items. It also features a terrible solution I sledgehammered into my code to deal with this for now.

[odelvalle]

Thanks @Flaniga3 but I can´t test this issue using external SQL Query. Please, can you post some test that help me to reproduce this "error" using only slapper.automapper?

[FilipFilipov]

I've found a test that better exemplifies the issue in ReadMeTests.

First change the models' Orders and OrderDetails properties from IList to Array, then try running I_Can_Map_Nested_Types_And_Resolve_Duplicate_Entries_Properly_Using_Dynamics. You will actually hit a different bug first, when trying to invoke the array's Contains method in MapCollection, because that's actually an extension method for arrays. The proper invocation in that case is something like:

MethodInfo containsMethod = typeof(Enumerable).GetMethods()
  .Single(m => m.Name == "Contains" && m.GetParameters().Length == 2)
  .MakeGenericMethod(type);
bool alreadyContainsInstance = (bool)containsMethod.Invoke(null,
  new[] { instance, instanceToAddToCollectionInstance });

Once you've done that, you should run into my original bug, as your mapped Customer will now have only one OrderDetails instead of two.