To use Linq : Except, Intersect, etc. on custom Class object collection, you need to provide IEqualityComparer, but is so frustrating, to write a class for each of your objects.
I have found that easiest way to avoid writing custom classes is to write one generic class:
public class Comparer<T> : IEqualityComparer<T>
{private readonly Func<T, T, bool> _comparer;
public Comparer(Func<T, T, bool> comparer)
{if (comparer == null) throw new ArgumentNullException("comparer");
_comparer = comparer;
}
public bool Equals(T x, T y)
{ return _comparer(x, y);}
public int GetHashCode(T obj)
{ return obj.ToString().ToLower().GetHashCode();}
}
and then You can write like this
IEnumerable<SPRoleAssignment> roles = fromRoles.Except(toRoles, new Comparer<SPRoleAssignment>((a, b) => a.Member.ID == b.Member.ID));