Shows how queries can be reused : Deferred Query « LINQ « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. LINQ
3. Deferred Query

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

public class MainClass {
    public static void Main() {
        int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
        var lowNumbers =
            from n in numbers
            where n <= 3
            select n;

        Console.WriteLine("First run numbers <= 3:");
        foreach (int n in lowNumbers) {
            Console.WriteLine(n);
        }

        for (int i = 0; i < 10; i++) {
            numbers[i] = -numbers[i];
        }

        Console.WriteLine("Second run numbers <= 3:");
        foreach (int n in lowNumbers) {
            Console.WriteLine(n);
        }
    }
}