I have problem with List<T>.Reverse()
and Reverse(this IEnumerable<TSource> source)
.
Look to the code:
// Part 1
List<int> list = new List<int> { 1, 2, 3 };
foreach (int x in list)
Console.Write(x);
Console.WriteLine();
list.Reverse();
foreach (int x in list)
Console.Write(x);
Console.WriteLine();
list.Reverse();
// Part2
IList<int> ilist = list;
foreach (int x in list)
Console.Write(x);
Console.WriteLine();
ilist.Reverse();
foreach (int x in ilist)
Console.Write(x);
Console.WriteLine();
ilist.Reverse();
My result:
123
321
123
123
because Reverse()
-Part1 is List<T>.Reverse()
, Reverse()
-Part2 is Reverse(this IEnumerable<TSource> source)
I want execute List<int>.Reverse()
in Part2 for IList<int>
. How I can do it?
IList<int>
doesn't have a Reverse
method, so it uses the extension method. The only way to use List<T>.Reverse
on your IList<int>
reference is to cast or convert it to a List<int>
. Casting will only work if you're sure that it's really a List<int>
in the first place:
IList<int> abstractList;
var concreteList = (List<int>)abstractList;
concreteList.Reverse();
Another option would be to create a List<int>
from your IList<int>
instance, rather than assuming it already is a List<int>
:
IList<int> abstractList;
var concreteList = new List<int>(abstractList);
concreteList.Reverse();
The reason that the Reverse
extension method doesn't actually affect the underlying list is because it operates on IEnumerable<T>
, which isn't necessarily writeable (none of the Enumerable
extension methods make changes to the original collection, they return a new collection).
To use this version of Reverse
, just use the product of the Reverse
call, rather than the original list:
IList<int> abstractList;
IEnumerable<int> reversedList = abstractList.Reverse();