Image a Person
and a Group
class with a many-to-many relationship. A person has a list of groups and a group has a list of people.
When mapping Person
to PersonDTO
I have a stack overflow exception
because AutoMapper can't handle the Person
>Groups
>Members
>Groups
>Members
>...
So here's the example code:
public class Person
{
public string Name { get; set; }
public List<Group> Groups { get; set; }
}
public class Group
{
public string Name { get; set; }
public List<Person> Members { get; set; }
}
public class PersonDTO
{
public string Name { get; set; }
public List<GroupDTO> Groups { get; set; }
}
public class GroupDTO
{
public string Name { get; set; }
public List<PersonDTO> Members { get; set; }
}
When I use .ForMember in creating a mapper, the first mapper that gets executed throws a null reference exception
.
Here's the code for the mapper:
CreateMap<Person, PersonDTO>()
.ForMember(x => x.Groups.Select(y => y.Members), opt => opt.Ignore())
.ReverseMap();
CreateMap<Group, GroupDTO>()
.ForMember(x => x.Members.Select(y => y.Groups), opt => opt.Ignore())
.ReverseMap();
So what am I missing or doing wrong? When I remove the .ForMember methods, the null reference exception
is not thrown anymore.
UPDATE: I really want to emphasize the main point of my question is how to ignore a property of a property. This code is just a rather simple example.
UPDATE 2: This is how I fixed it, big thanks to Lucian-Bargaoanu
CreateMap<Person, PersonDTO>()
.ForMember(x => x.Groups.Select(y => y.Members), opt => opt.Ignore())
.PreserveReferences() // This is the solution!
.ReverseMap();
CreateMap<Group, GroupDTO>()
.ForMember(x => x.Members.Select(y => y.Groups), opt => opt.Ignore())
.PreserveReferences() // This is the solution!
.ReverseMap();
Thanks to .PreserveReferences()
the circular references get fixed!
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