using System;           

using System.Security.Cryptography;

using System.Text;

​

public class Program

{   

    public static void Main()

    {

        Console.WriteLine(HmacSha256("tést", "xxx"));

        Console.WriteLine(HMACSHA256Encrypt("tést", "xxx"));

    }

    public static string HmacSha256(string str, string key)

    {

        var arrKey = Encoding.UTF8.GetBytes(key);

        var message = Encoding.UTF8.GetBytes(str);

        var hmac = new HMACSHA256(arrKey);

        return Convert.ToHexString(hmac.ComputeHash(message)).ToLower();

    }

    public static String HMACSHA256Encrypt(String text, String key)

    {

        Byte[] textBytes = Encoding.UTF8.GetBytes(text);

        Byte[] keyBytes = Encoding.UTF8.GetBytes(key);

        Byte[] hashBytes;

​

        using (HMACSHA256 hash = new HMACSHA256(keyBytes))

            hashBytes = hash.ComputeHash(textBytes);

​

        return BitConverter.ToString(hashBytes).Replace("-", "").ToLower();

    }

}