Setting IsCollection on TypeDescriptor with Name '{0}' and Id '{1}' (belonging to Parameter with Name '{2}' and Id '{3}') ...

Setting IsCollection on TypeDescriptor with Name '{0}' and Id '{1}' (belonging to Parameter with Name '{2}' and Id '{3}') will create two consecutive parent-child TypeDescriptors that have 'IsCollection' set. Collection TypeDescriptors may only have a single child TypeDescriptor, representing the structure of each element of the collection.