Initial data commit

Task/SQL-based-authentication/C-sharp/sql-based-authentication-2.cs

@@ -0,0 +1,65 @@
+using MySql.Data.MySqlClient;
+
+namespace rosettaMySQL
+{
+    class UserOperator
+    {
+        private MySqlConnection _connection;
+
+        public UserOperator(MySqlConnection connection)
+        {
+            _connection = connection;
+        }
+
+        public bool CreateUser(string username, string password)
+        {
+            try
+            {
+                var salt = Hasher.GenSalt();
+                var hash = Hasher.Hash(salt, password);
+                var sql = $"INSERT INTO users " +
+                          $"(username, pass_salt, pass_md5) " +
+                          $"VALUES ('{username}','{salt}','{hash}')";
+                using (var command = new MySqlCommand(sql, _connection))
+                {
+                    command.ExecuteNonQuery();
+                    return true;
+                }
+            }
+            catch (MySqlException e)
+            {
+                if (e.Number == 1062) //username is a duplicate
+                {
+                    return false;
+                }
+                else
+                {
+                    throw e;
+                }
+            }
+        }
+
+        public bool AuthenticateUser(string username, string password)
+        {
+            var sql = $"SELECT userid, username, pass_salt, pass_md5 " +
+                      $"FROM users " +
+                      $"WHERE username='{username}';";
+
+            using (var command = new MySqlCommand(sql, _connection))
+            using (var reader = command.ExecuteReader())
+            {
+                if (reader.HasRows)
+                {
+                    reader.Read();
+                    var salt = reader.GetString("pass_salt");
+                    var hash = reader.GetString("pass_md5");
+                    return (Hasher.Hash(salt, password) == hash);
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
+    }
+}