How to generate HMAC-SHA1 in C#?

  using (HMACSHA1 m = new HMACSHA1(Encoding.UTF8.GetBytes("AKIDZfbOA78asKUYBcXFrJD0a1ICvR98JM")))
            {
                var result = BitConverter.ToString(m.ComputeHash(Encoding.UTF8.GetBytes("1480932292;1481012292"))).Replace("-", "").ToLower();
                textBox1.Text = result;
            }