using System;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        string name = "developer@example.com";

        char[] vowels = new char[]{'A', 'E', 'I', 'O', 'U', 'a', 'e', 'i', 'o', 'u'};

        int vowelsCount = 0;

        //2D for loop

        for (int i = 0; i < name.Length; i++)

        {

            for (int j = 0; j < vowels.Length; j++)

                if (name[i] == vowels[j])

                    vowelsCount++;

        }

​

        Console.WriteLine($"{vowelsCount} vowels found");

        //using methods of arrays/collections

        vowelsCount = 0;

        for (int i = 0; i < name.Length; i++)

        {

            if (Array.IndexOf(vowels, name[i]) >= 0)

                vowelsCount++;

        }

​

        Console.WriteLine($"{vowelsCount} vowels found");

        //using LINQ -> single line of code

        vowelsCount = name.Count(ch => Array.IndexOf(vowels, ch) >= 0);

        Console.WriteLine($"{vowelsCount} vowels found");

    }

}