Lambda and Linq

Most query operators accept a lambda expression as an argument.

 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
class Program
{
    static void Main()
    {
        string[] names = { "C", "Java", "C#", "Javascript" };
        IEnumerable<string> filteredNames = System.Linq.Enumerable.Where(names, n => n.Length >= 4);
        foreach (string n in filteredNames)
            Console.WriteLine(n);
    }
}

The output:


Java
Javascript

In example above, the lambda expression is as follows:


n => n.Length >= 4

The input argument corresponds to an input element.

n represents each name in the array and is of type string.

The Where operator requires that the lambda expression return a bool value, which if true, indicates that the element should be included in the output sequence.

Here's its signature:

 
public static IEnumerable<TSource> Where<TSource>
              (this IEnumerable<TSource> source, Func<TSource,bool> predicate)

The following query retrieves all names that contain the letter "a":

 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
class Program
{
    static void Main()
    {
        string[] names = { "C", "Java", "C#", "Javascript" };

        IEnumerable<string> filteredNames = names.Where(n => n.Contains("a"));

        foreach (string name in filteredNames)
            Console.WriteLine(name);
    }
}

The output:


Java
Javascript

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