This task has three parts:

 Connect to a MySQL database (connect_db)
 Create user/password records in the following table (create_user)
 Authenticate login requests against the table (authenticate_user)
This is the table definition:

CREATE TABLE users (
    userid INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(32) UNIQUE KEY NOT NULL,
    pass_salt tinyblob NOT NULL,
            -- a string of 16 random bytes
    pass_md5 tinyblob NOT NULL
            -- binary MD5 hash of pass_salt concatenated with the password
);
(pass_salt and pass_md5 would be binary(16) values, but MySQL versions before 5.0.15 strip trailing spaces when selecting them.)

using System.Security.Cryptography;
using System.Text;
 
namespace rosettaMySQL
{
    class Hasher
    {
        private static string _BytesToHex(byte[] input)
        {
            var strBuilder = new StringBuilder();
            foreach (byte _byte in input)
            {
                strBuilder.Append(_byte.ToString("x2"));
            }
            return strBuilder.ToString();
        }
 
        public static string Hash(string salt, string input)
        {
            using (MD5 md5 = new MD5CryptoServiceProvider())
            {
                var bytes = Encoding.Default.GetBytes(salt + input);
                var data = md5.ComputeHash(bytes);
                return _BytesToHex(data);
            }
        }
 
        public static string GenSalt()
        {
            using (RandomNumberGenerator rng = new RNGCryptoServiceProvider())
            {
                var salt = new byte[16];
                rng.GetBytes(salt);
                return _BytesToHex(salt);
            }
        }
    }
}