Count the Vowels in C#

Given a string s, return how many vowels it has.

The vowels are a, e, i, o and u, in lower case or in upper case. The letter y is not a vowel here. Every other character (consonants, spaces, digits, punctuation) is skipped.

Example 1:

Input: s = "Hello World"
Output: 3
Explanation: The vowels are e, o and o. The other characters, the space included, are skipped.

Example 2:

Input: s = "AlgoCademy"
Output: 4
Explanation: A, o, a and e are vowels: the upper-case A counts too. The y doesn't count.

Example 3:

Input: s = "Why try?"
Output: 0
Explanation: y is not a vowel, so this string has none.

Constraints:

• s has at least one character and doesn't start or end with a space.
• s contains English letters, digits, spaces and punctuation.