Linq- Partitioning Operators (Take, Skip, TakeWhile, SkipWhile)

The following 4 standard LINQ query operators belong to Partitioning Operators category
Take, Skip, TakeWhile, SkipWhile

Take method returns a specified number of elements from the start of the collection. The number of items to return is specified using the count parameter this method expects.

Skip method skips a specified number of elements in a collection and then returns the remaining elements. The number of items to skip is specified using the count parameter this method expects. 

Please Note: For the same argument value, the Skip method returns all of the items that the Take method would not return.

TakeWhile method returns elements from a collection as long as the given condition specified by the predicate is true. 

SkipWhile method skips elements in a collection as long as the given condition specified by the predicate is true, and then returns the remaining elements.

Example 1: Retrieves only the first 3 countries of the array.

string[] countries = { "Australia", "Canada", "Germany", "US", "India", "UK", "Italy" };

IEnumerable<string> result = countries.Take(3);

foreach (string country in result)

{

    Console.WriteLine(country);

}

Example 2: Rewrite Example 1 using SQL like syntax

string[] countries = { "Australia", "Canada", "Germany", "US", "India", "UK", "Italy" };

IEnumerable<string> result = (from country in countries

                                                   select country).Take(3);

foreach (string country in result)

{

    Console.WriteLine(country);

}

Example 3: Skips the first 3 countries and retrieves the rest of them

string[] countries = { "Australia", "Canada", "Germany", "US", "India", "UK", "Italy" };

IEnumerable<string> result = countries.Skip(3);

foreach (string country in result)

{

    Console.WriteLine(country);

}

Example 4: Return countries starting from the beginning of the array until a country name is hit that does not have length greater than 2 characters.

string[] countries = { "Australia", "Canada", "Germany", "US", "India", "UK", "Italy" };

IEnumerable<string> result = countries.TakeWhile(s => s.Length > 2);

foreach (string country in result)

{

    Console.WriteLine(country);

}

Example 5: Skip elements starting from the beginning of the array, until a country name is hit that does not have length greater than 2 characters, and then return the remaining elements.

string[] countries = { "Australia", "Canada", "Germany", "US", "India", "UK", "Italy" };

IEnumerable<string> result = countries.SkipWhile(s => s.Length > 2);

foreach (string country in result)

{

    Console.WriteLine(country);

}

Posted in: LINQ