Conditional "orderby" sort order in LINQ

user_82 0
Viewed 53089

In LINQ, is it possible to have conditional orderby sort order (ascending vs. descending).

Something like this (not valid code):

bool flag;

(from w in widgets
 where w.Name.Contains("xyz")
 orderby w.Id (flag ? ascending : descending)
 select w)
linq .net c#
9 Answers

...Or do it all in one statement

bool flag;

var result = from w in widgets where w.Name.Contains("xyz")
  orderby
    flag ? w.Id : 0,
    flag ? 0 : w.Id descending
  select w;
user_3244790

Can also roll up Richard's answer into a convenient helper method, like so:

internal static class LinqExtensions
{
    public static IOrderedEnumerable<TSource> OrderBy<TSource,TKey>
        (this IEnumerable<TSource> source,
         Func<TSource, TKey> keySelector,
         bool ascending)
    {
        return ascending ? source.OrderBy(keySelector)
                         : source.OrderByDescending(keySelector);
    }

    public static IOrderedEnumerable<TSource> ThenBy<TSource,TKey>
        (this IOrderedEnumerable<TSource> source,
         Func<TSource, TKey> keySelector,
         bool ascending)
    {
        return ascending ? source.ThenBy(keySelector)
                         : source.ThenByDescending(keySelector);
    }
}
user_189750280
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