removing duplicates from a list C#

Question

I am following a previous post on stackoverflow about removing duplicates from a List in C#.

If is some user defined type like:

Answer 1

For this task I don't necessarily thinks implementing IComparable is the obvious solution. You might want to sort and test for uniqueness in many different ways.

I would favor implementing a IEqualityComparer:

sealed class ContactFirstNameLastNameComparer : IEqualityComparer
{
  public bool Equals (Contact x, Contact y)
  {
     return x.firstname == y.firstname && x.lastname == y.lastname;
  }

  public int GetHashCode (Contact obj)
  {
     return obj.firstname.GetHashCode () ^ obj.lastname.GetHashCode ();
  }
}

And then use System.Linq.Enumerable.Distinct (assuming you are using at least .NET 3.5)

var unique = contacts.Distinct (new ContactFirstNameLastNameComparer ()).ToArray ();

PS. Speaking of HashSet<> Note that HashSet<> takes an IEqualityComparer<> as a constructor parameter.