Question

If have a class of Widgets like this:

public class Widget
{
   public double Price { get; set; }
   public string Type { get; set; }
   public int ID { get; set; }
   public string Name { get; set; }
}

And create a list of them:

List<Widget> Widgets = new List<Widget>
   {
       new Widget {ID = 1, Name = "One", Price = 3.00, Type = "Gooy"},
       new Widget {ID = 2, Name = "Two", Price = 5.00, Type = "Crispy"},
       new Widget {ID = 2, Name = "Three", Price = 3.00, Type = "Hard"},
       new Widget {ID = 2, Name = "Four", Price = 3.00, Type = "Chewy"},
       new Widget {ID = 2, Name = "Five", Price = 2.50, Type = "Gooy"}
   };

And then I call IEnumerable.Distinct with a custom comparer like so:

IEqualityComparer<Widget> widgetComparer = 
   new LambdaComparer<Widget>((item1, item2) => item1.Price == item2.Price);

Widgets.Distinct(widgetComparer);

Then (as I see it) there should be 3 objects returned (one for each price category).

What is the Type of the 3.00 one (Gooy, Hard or Chewy)?

Does it pick one? (I am trying to understand distinct better because my real distinct is not giving me distinct results.)

Answer 1

Distinct takes whatever the comparer determines; so if there are 3 different objects with the same price, and your custom comparer only looks at the price, then it should consider them one and the same, depending on how the comparison takes place.

HTH.