C# 3.0: Need to return duplicates from a List<>

Question

I have a List<> of objects in C# and I need a way to return those objects that are considered duplicates within the list. I do not need the Distinct resultset, I need a

Answer 1

My answer takes inspiration (in this order) from the followers respondents: Joe Coehoorn, Greg Beech and Jon Skeet.

I decided to provide a full example, with the assumption being (for real word efficiency) that you have a static list of car colors. I believe the following code illustrates a complete solution to the problem in an elegant, although not necessarily hyper-efficient, manner.

#region SearchForNonDistinctMembersInAGenericListSample
public static string[] carColors = new[]{"Red", "Blue", "Green"}; 
public static string[] carStyles = new[]{"Compact", "Sedan", "SUV", "Mini-Van", "Jeep"}; 
public class Car
{
    public Car(){}
    public string Color { get; set; }
    public string Style { get; set; }
}
public static List SearchForNonDistinctMembersInAList()
{
    // pass in cars normally, but declare here for brevity
    var cars = new List(5) { new Car(){Color=carColors[0], Style=carStyles[0]}, 
                                      new Car(){Color=carColors[1],Style=carStyles[1]},
                                      new Car(){Color=carColors[0],Style=carStyles[2]}, 
                                      new Car(){Color=carColors[2],Style=carStyles[3]}, 
                                      new Car(){Color=carColors[0],Style=carStyles[4]}};
    List carDupes = new List();

    for (int i = 0; i < carColors.Length; i++)
    {
        Func dupeMatcher = c => c.Color == carColors[i];

        int count = cars.Count(dupeMatcher);

        if (count > 1) // we have duplicates
        {
            foreach (Car dupe in cars.Where(dupeMatcher).Skip(1))
            {
                carDupes.Add(dupe);
            }
        }
    }
    return carDupes;
}
#endregion

I'm going to come back through here later and compare this solution to all three of its inspirations, just to contrast the styles. It's rather interesting.