using System;

using System.Security.Cryptography;

public class Program

{

    public static byte[] FromHex(string hex)

    {

        hex = hex.Replace("-", "");

        byte[] raw = new byte[hex.Length / 2];

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

        {

            raw[i] = Convert.ToByte(hex.Substring(i * 2, 2), 16);

        }

        return raw;

    }

​

    public static void Main()

    {

        string message = @"{""requestDateTime"": ""20190613160913"",""personalId"": ""A123456789""}";

        byte[] keyByte = FromHex("3050564e6b6e6539476e7974305972714e394e567177627a4548774232474a42");

        var encoding = new System.Text.ASCIIEncoding();

        byte[] messageBytes = encoding.GetBytes(message);

        using (var hmacsha256 = new HMACSHA256(keyByte))

        {

            byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);

            Console.WriteLine(BitConverter.ToString(hashmessage).Replace("-", "").ToLower());

        }

    }

}