I have the below implementation.

members.RemoveAll doesn't seem to be doing the job by the way. I wonder why and how to fix this. thanks!

public class Member
{
    public string member { get; set; }
}

public class SpecialMember
{
    public string Upn { get; set; }
}

public class RemoveFromList
{
    public static List<Member> Remove()
    {
        var specialMembers = new List<SpecialMember>();
        specialMembers.Add(new SpecialMember { Upn = "[email protected]" });

        var members = new List<Member>();
        members.Add(new Member { member = "[email protected]" });
        members.Add(new Member { member = "[email protected]" });

        var toRemove = members.Select(f => f.member)
                              .Intersect(specialMembers.Select(s => s.Upn))
                              .Select(m => new Member
                              {
                                  member = m
                              }).ToList();


        members.RemoveAll(m =>
        {
            var b = toRemove.Contains(m);
            return b;
        });

        return members;
    }
}

CodePudding user response：

The problem is that you create new Member instances in the Select, so Object.ReferenceEquals doesn't return true anymore and your Contains logic fails. You could simplify the whole code to:

members.RemoveAll(m => specialMembers.Select(sm => sm.Upn).Contains(m.member));