using System;

using System.Security.Cryptography;

using System.Text;

const string apiKey = "Hello, World!";

​

var hasher = SHA256.Create();

var hashAsBytes = Encoding.UTF8.GetBytes(apiKey);

var hash = hasher.ComputeHash(hashAsBytes);

var hashAsHex = Convert.ToHexString(hash).ToLower();

Console.WriteLine(hashAsHex);

​