What Sorting Algorithm Is Used By LINQ "OrderBy"?

Solution 1:

For LINQ to Objects, it's a stable quicksort that is used. For any other kind of LINQ, it's left to the underlying implementation.

Solution 2:

Boot up reflector, open to System.Linq.EnumerableSorter reveals that Linq2Objects uses the quick sort

Solution 3:

Quicksort is used, but the reason why it is stable is because the indices of each pair of elements are compared if all the keys test equal.

In other words, you can make any quicksort stable by including in the comparator function a comparison of the original indices of the two elements as a fallback.

Source: http://referencesource.microsoft.com/#System.Core/System/Linq/Enumerable.cs,1395017e067e5a34

Solution 4:

I am under the understanding that OrderBy gets translated into SQL that performs the sort on the Database. At least in the case of LINQ to SQL