Take and Skip
Learn slicing with Take, Skip, TakeWhile and SkipWhile.
Slicing with Take and Skip
Take(n) takes the first n elements of a collection. Skip(n) skips the first n and returns the rest. Both are deferred; the result is again an IEnumerable<T>.
For pagination you combine them: 5 items on page 2 is items.Skip(5).Take(5). This pattern also shows up in database queries. Taking more than available is safe; Take returns what it has.
TakeWhile and SkipWhile
TakeWhile(condition) takes elements from the start as long as the condition holds; it stops at the first mismatch. SkipWhile(condition) skips from the start as long as the condition holds; it returns everything from the first mismatch onward.
Example: new[] { 2, 4, 6, 7, 8 }.TakeWhile(n => n % 2 == 0) yields { 2, 4, 6 }; 7 is odd, so it stops. These methods are useful for finding patterns in ordered data.
Exercise Take the first three
Take the first three elements of numbers with Take(3) and print each in a foreach loop.
Show example solution
Take the first three with numbers.Take(3), loop with foreach, print with Console.WriteLine(n).
Example solution:
using System;
using System.Linq;
class Program
{
static void Main()
{
int[] numbers = { 10, 20, 30, 40, 50 };
foreach (var n in numbers.Take(3))
{
Console.WriteLine(n);
}
}
}Test yourself
-
How is pagination done?
- Take(5).Skip(5)
- Skip(5).Take(5)
- Skip(5).Distinct()
- Take(5).Where(...)
Show answer
Skip(5).Take(5) — Correct. First Skip past the earlier pages, then Take the items of the target page.
-
Match each method to its result
- Take(3)
- First three
- Skip(3)
- Skip first three
- TakeWhile(...)
- Until break
- SkipWhile(...)
- After break
-
Complete the Take call
var first3 = numbers.____(3);Show answer
var first3 = numbers.Take(3);