How to find the second greatest element in a list with LINQ

Question

Suppose we have a class (SomeClass) with two fields, an ID of type int and a date of type DateTime.

Now imagine that there is a list of SomeClass ordered by date and we need to find the second to last element of the list. How would we do this with LINQ ?

Answer 1

var nextToLast = list.Skip(list.Count - 2).First();

正如@Brizio指出的那样，您也可以使用良好的索引

var nextToLast = list[list.Count - 2];

Answer 2

Here is one for the second place:

In your comparison:

public class YourCustomClassComparer : IComparer<YourObject> {
    public int Compare(YourObject x, YourObject y) {
        //do whatever you need to do to compare
    }
}

and your method (this will grab the second in the list)

var result = list.OrderBy(a => a, new YourCustomClassCompairer()).ElementAt(1);

And if you wanted the inverse (which i noticed in your question), do the following

var result = list.OrderByDescending(a => a, new YourCustomClassCompairer()).ElementAt(1);