I was wondering if there is possibility to use singleton as comparerObject in for example Distinct ??
Let's say that I have a list of element and I need to use distinct function on that list. Normally I would do that this way
var result = list.Distinct(new ListElementComparer);
ListElementCo开发者_如何学JAVAmparer is a class which implements IEqualityComparer interface. However let's assume that I will be using code mentioned above quite frequently for example that way .
List<List<Element>> elementList = new List<List<Elements>>();
List<List<Element>> resultList new List<List<Element>>();
foreach(var element in elementList )
resultList.AddRange(element.Distinct(new ListElementComparer() ) );
So as You can object of ListElementComparer might be created quite a lot of times. In this case is there any point of using singletone insted of createing ListElementComparer in each iteration ? Will the distinct method work if I use singleton ??
Yes, absolutely, it will work fine with a singleton:
public class ListElementComparer : IEqualityComparer<List<Element>>
{
public static ListElementComparer Instance { get { return instance; } }
private static readonly ListElementComparer instance =
new ListElementComparer();
private ListElementComparer() {}
// Implement IEqualityComparer<List<Element>> here
}
Then:
resultList.AddRange(element.Distinct(ListElementComparer.Instance);
Note that your whole loop can be avoided somewhat:
var resultList = elementList
.SelectMany(x => x.Distinct(ListElementComparer.Instance))
.ToList();
(This doesn't quite work with the originally-declared types, because your sample code doesn't quite work either... but something similar would.)
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