8.24.2012

Difference between Skip() and SkipWhile() extension methods in LINQ

Difference between Skip() and SkipWhile() extension methods in LINQ
S.No Skip() SkipWhile()
1
Skip() will take an integer argument and skips the top n numbers from the given IEnumerable
SkipWhile() continues to skip the elements as long as the input condition is true. Once condition turns false it will return all remaining elements.

2.Signature of Skip ():

public static IEnumerable Skip( this IEnumerable source, int count);

3.Example:

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

var firstNumbersLessThan6 = numbers.Skip(3);

In this example, the Skip method will skip the first 3 items from the collection and return the remaining items as an IEnumerable collection.
So the output of this example will be 3, 9, 8, 6, 7, 2 and 0.
2a.Signature of SkipWhile ():

public static IEnumerable SkipWhile( this IEnumerable source, =unc predicate);

2b.Another signature for overriding:

public static IEnumerable SkipWhile( this IEnumerable source, Func predicate);

3a.Example I:

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7 };

var remaining = numbers.SkipWhile(n => n < 9);

In this example the SkipWhile operator will skip the items from the starting position until the conditions fails. Once the condition has failed then it will return the remaining items as an IEnumerable collection.

So the output for this example is 9, 8, 6 and 7.

3b.Example II:

int[] numbers = { 5, 4, 1, 3, 9, 8, 2, 0 };

var indexed = numbers.SkipWhile((n, index) => n > index);

In this example the SkipWhile method will skip the items greater than their positions.

So in this example the output is 1, 3, 9, 8, 2 and 0. Because the position of the 1 is 2 so here the condition fails.

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