Encriptación con C#

//AGREGAR EL SIGUIENTE USING
//using System.Security.Cryptography;

string login_pass = textBox3.Text;
MD5 md5 = MD5.Create();
byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(login_pass );
byte[] hash = md5.ComputeHash(inputBytes);
login_pass = BitConverter.ToString(hash).Replace("-", "");