30 Days Of .NET 6 - Day 11 - LINQ Improvements - Range Support

One of the most powerful features of LINQ is the ability to select a range of elements from a collection.

This is accomplished using the Take and Skip LINQ expressions, and their derivatives (TakeLast, SkipLast) that allow you to specify what you want (Take) and what to discard (Skip).

These work perfectly well, but can be a bit ungainly.

A very welcome improvement is now that LINQ supports range operators operators.

These allow you to specify very tersely what values you want to pull out of a something.

These were previously defined for strings and arrays, but now in .NET 6 this has been extended to any collection that implements IEnumerable which is most collections.

This is best explained using examples that demonstrate use.

Assuming you have the following array:

var numbers = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };

Tip - you can also get an equivalent range of numbers quickly using Enumerable.Range as follows:

var numbers = Enumerable.Range(1, 15);

Following are a bunch of expressions to query this data demonstrating the traditional query technique and the new technique.

To get the last 5 numbers:

var oldLastFive = numbers.TakeLast(5);
var newLastFive = numbers.Take(^5..);

This should return:

11,12,13,14,15

A bit more elaborate: to get 5 numbers and then skip 2

var oldTakeFiveSkipTwo = numbers.Take(5).Skip(2);
var newTakeFiveSkipTwo = numbers.Take(2..5);

This should return

3,4,5

You need to be very careful about the order! The order in which you Take and Skip matters! Consider this expression:

numbers.Take(2).Skip(5);

If you Take 2 elements first, and then proceed to Skip 5 from the 2 you have taken, your resulting collection will be empty!

To get all the elements except the first 5:

var oldSkipFive = numbers.Skip(5);
var newSkipFive = numbers.Take(5..);

This should return

6,7,8,9,10,11,12,13,14,15

To get all the elements except the last 5:

var oldSkipLastFive = numbers.SkipLast(5);
var newSkipLastFive = numbers.Take(..^5);

To get the last 10 elements, and then skip the last 5 of those:

var oldLastTenSkipLast5 = numbers.TakeLast(10).SkipLast(5);
var newLastTenSkipLast5 = numbers.Take(^10..^5);

Thoughts

This is a great addition to the LINQ engine.

The code is in my Github

TLDR

Index and range support to LINQ makes it easier to write more expressive queries when managing collections.

This is Day 11 of the 30 Days Of .NET 6 where every day I will attempt to explain one new / improved thing in the upcoming release of .NET 6.

Happy hacking!