LINQ Operators: Projection Operators

In previous article we discussed about Filtering operators in LINQ. So moving forward today we will see the Projection Operators in LINQ. 

Projection Operators

LINQ has two projection operators namely Select and SelectMany.

1. Select- Just like Select in SQL, Select operator returns specified elements. Select operator returns one output element for each input element. The record or data retrieval based on two models. One is element based selection and another one is Index based selection.
   Index based:
   

   int[] digits = { 1, 5, 6, 2, 0 };

   string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

   var textNums = from n in digits

                  select strings[n]; /*one five six two zero*/

   
   

   Element based:

   string[] strings = { "zero", "one", "two", "three" };

   
   

   var query= from s in strings

   
   

              select s; /*zero one two three*/ 
2. SelectMany- The SelectMany operator is useful when you are working on sequence of sequences. SelectMany concatenates sub sequences into a single flat output sequence. The SQL equivalent of SelectMany is INNER JOIN, LEFT OUTER JOIN and CROSS JOIN. 
      string[] famousQuotes = {"Advertising is legalized lying",

   "Advertising is the greatest art form of the twentieth century"};

   var query =   famousQuotes.SelectMany(s => s.Split(' ')).Distinct();

     

   /*Output

   Advertising

   is

   legalized

   lying

   the

   greatest

   art

   form

   of

   twentieth

   century
   

   */

To be continude.....

Happy reading!!