public static int Register(string login, string password)
        {
            SqlConnection sqlConn = new SqlConnection(connectionString());
            //File.WriteAllText(@"c:\a\b\debug.txt", LoginVariables.connectionString());
            int ID = 0;
            try
            {
                sqlConn.Open();
                SqlCommand cmd = new SqlCommand("SELECT ID_User FROM Users WHERE Login_user=@Name_profile AND Password_user=@Password_profile", sqlConn);
                cmd.Parameters.AddWithValue("@Name_profile", login);
                cmd.Parameters.AddWithValue("@Password_profile", password);
                //File.WriteAllText(@"c:\a\b\error.txt", command.CommandText);
                ID = (Int32)cmd.ExecuteScalar();
                Console.WriteLine("Podany uzytkownik istnieje już w bazie danych podaj inne hasło.");

            }
            catch (System.NullReferenceException se)
            {
                SqlCommand command = new SqlCommand("INSERT INTO Users (Login_user, Password_user, Name) VALUES (@Name_profile, @Password_profile, @Name_profile)", sqlConn);
                command.Parameters.AddWithValue("@Name_profile", login);
                command.Parameters.AddWithValue("@Password_profile", password);
                command.ExecuteNonQuery();
                Console.WriteLine("Konto zostało utworzone. " + Environment.NewLine + "Login : " + login + Environment.NewLine + "Password : " + password);
                SqlCommand cmd = new SqlCommand("SELECT ID_User FROM Users WHERE Login_user=@Name_profile", sqlConn);
                cmd.Parameters.AddWithValue("@Name_profile", login);
                //File.WriteAllText(@"c:\a\b\error.txt", command.CommandText);
                ID = (Int32)cmd.ExecuteScalar();
                Console.WriteLine("ID: " + ID);
            }
            catch (System.Data.SqlClient.SqlException se)
            {
            }
            return ID;
        }