public void RemoveComplexType(SomeComplexType item)
        {
            // ...shortened for example.

            AComplexTypeArray = AComplexTypeArray.Except(new[] { item }).ToArray();
        }
        public void AddComplexType(SomeComplexType item)
        {
            // ...shortened for example.

            AComplexTypeArray = AComplexTypeArray.Append(item).ToArray();
        }