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Select

Input:	IEnumerable<TSource>
Lamdbda expression:	TSource => TResult or (TSource,int) => TResult
Query syntax:	select projectionExpression

Select returns the same number of elements as the input.

 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        string[] names = { "Java", "C#", "Javascript", "SQL", "Oracle", "Python", "C++", "C", "HTML", "CSS" };

        IEnumerable<string> query = from n in names select n.ToLower();
        foreach(String s in query){
           Console.WriteLine(s);
        }
    }
}

The output:


java
c#
javascript
sql
oracle
python
c++
c
html
css

Indexed projection

The select operator can accept an integer argument as an indexer.

This works only with local queries:

 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        string[] names = { "Java", "C#", "Javascript", "SQL", "Oracle", "Python", "C++", "C", "HTML", "CSS" };

        IEnumerable<string> query = names.Select((s, i) => i + "=" + s);
        foreach(String s in query){
           Console.WriteLine(s);
        }
    }
}

The output:


0=Java
1=C#
2=Javascript
3=SQL
4=Oracle
5=Python
6=C++
7=C
8=HTML
9=CSS

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