C#•17mo ago

❔ login system saves data from user

Hi this is the code that i have and i dont know why but its showing me the username and not the realname on the label, why? Button on Form1 to check if user credentials are correct and if user exists open MainMenu and display the realname of the user logged in.

private void btnEntrar_Click(object sender, EventArgs e)
        {
            string connectionString = "Data Source=(localdb)\\MSSqlLocalDB;Initial Catalog=oil;Integrated Security=True;Pooling=False";
            string username = txtUsername.Text;
            string password = txtPassword.Text;
            UserData loggedInUser = null;

            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();

                SqlCommand command = new SqlCommand("SELECT * FROM Users WHERE username = @username AND password = @password", connection);
                command.Parameters.AddWithValue("@username", username);
                command.Parameters.AddWithValue("@password", password);

                SqlDataReader reader = command.ExecuteReader();

                if (reader.HasRows)
                {
                    reader.Read();
                    int id = reader.GetInt32(0);
                    string realname = reader.GetString(1);
                    string nivel = reader.GetString(2);

                    // create a new User object with the retrieved data
                    loggedInUser = new UserData(id, realname, nivel);

                    // open the main menu form
                    MainMenu mainMenu = new MainMenu(loggedInUser);
                    mainMenu.Show();
                    this.Hide();
                }
                else
                {
                    // invalid credentials, display error message
                    MessageBox.Show("Credenciais inválidas!");
                }

                reader.Close();
            }
        }

private void btnEntrar_Click(object sender, EventArgs e)
        {
            string connectionString = "Data Source=(localdb)\\MSSqlLocalDB;Initial Catalog=oil;Integrated Security=True;Pooling=False";
            string username = txtUsername.Text;
            string password = txtPassword.Text;
            UserData loggedInUser = null;

            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();

                SqlCommand command = new SqlCommand("SELECT * FROM Users WHERE username = @username AND password = @password", connection);
                command.Parameters.AddWithValue("@username", username);
                command.Parameters.AddWithValue("@password", password);

                SqlDataReader reader = command.ExecuteReader();

                if (reader.HasRows)
                {
                    reader.Read();
                    int id = reader.GetInt32(0);
                    string realname = reader.GetString(1);
                    string nivel = reader.GetString(2);

                    // create a new User object with the retrieved data
                    loggedInUser = new UserData(id, realname, nivel);

                    // open the main menu form
                    MainMenu mainMenu = new MainMenu(loggedInUser);
                    mainMenu.Show();
                    this.Hide();
                }
                else
                {
                    // invalid credentials, display error message
                    MessageBox.Show("Credenciais inválidas!");
                }

                reader.Close();
            }
        }

11 Replies

yumo•17mo ago

This is what i have on MainMenu form

private UserData loggedInUser;
        public MainMenu(UserData user)
        {
            InitializeComponent();
            loggedInUser = user;

            // display the logged-in user's first name on the lblNomeUtilizador label
            lblNomeUtilizador.Text = loggedInUser.RealName;
        }

private UserData loggedInUser;
        public MainMenu(UserData user)
        {
            InitializeComponent();
            loggedInUser = user;

            // display the logged-in user's first name on the lblNomeUtilizador label
            lblNomeUtilizador.Text = loggedInUser.RealName;
        }

And this is my UserData class to save the information of the user

public class UserData
    {
        public int UserId { get; set; }
        public string RealName { get; set; }
        public string Nivel { get; set; }

        public UserData(int id, string realname, string nivel)
        {
            UserId = id;
            RealName = realname;
            Nivel = nivel;
        }

    }

public class UserData
    {
        public int UserId { get; set; }
        public string RealName { get; set; }
        public string Nivel { get; set; }

        public UserData(int id, string realname, string nivel)
        {
            UserId = id;
            RealName = realname;
            Nivel = nivel;
        }

    }

Angius•17mo ago

Use the debugger, see if the variables you get from the database are what you think they are That's why I recommend using Dapper at least, instead of having to fuck around with loosely-typed readers

yumo•17mo ago

idk hwo to work with dapper mb

Angius•17mo ago

Easier than with ADO that's for sure

mikernet•17mo ago

It's better to select the columns instead of relying on the order that * returns them in

yumo•17mo ago

This? SELECT realname FROM Users WHERE username = @username AND password = @password ?

mikernet•17mo ago

Well you're reading 3 columns So select 3 columns id, realname, nivel

yumo•17mo ago

Something like this

using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();

                SqlCommand command = new SqlCommand("SELECT realname, id, nivel FROM Users WHERE  username = @username AND password = @password", connection);
                command.Parameters.AddWithValue("@username", username);
                command.Parameters.AddWithValue("@password", password);

                SqlDataReader reader = command.ExecuteReader();

                if (reader.HasRows)
                {
                    reader.Read();
                    int id = reader.GetInt32(0);
                    string realname = reader.GetString(1);
                    string nivel = reader.GetString(2);

                    // create a new User object with the retrieved data
                    loggedInUser = new UserData(id, realname, nivel);

                    // open the main menu form
                    MainMenu mainMenu = new MainMenu(loggedInUser);
                    mainMenu.Show();
                    this.Hide();
                }
                else
                {
                    // invalid credentials, display error message
                    MessageBox.Show("Credenciais inválidas!");
                }

                reader.Close();
            }

using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();

                SqlCommand command = new SqlCommand("SELECT realname, id, nivel FROM Users WHERE  username = @username AND password = @password", connection);
                command.Parameters.AddWithValue("@username", username);
                command.Parameters.AddWithValue("@password", password);

                SqlDataReader reader = command.ExecuteReader();

                if (reader.HasRows)
                {
                    reader.Read();
                    int id = reader.GetInt32(0);
                    string realname = reader.GetString(1);
                    string nivel = reader.GetString(2);

                    // create a new User object with the retrieved data
                    loggedInUser = new UserData(id, realname, nivel);

                    // open the main menu form
                    MainMenu mainMenu = new MainMenu(loggedInUser);
                    mainMenu.Show();
                    this.Hide();
                }
                else
                {
                    // invalid credentials, display error message
                    MessageBox.Show("Credenciais inválidas!");
                }

                reader.Close();
            }

But displaying this error: System.InvalidCastException: 'The specific conversion isnt valid.' on this line: int id = reader.GetInt32(0);

mikernet•17mo ago

Thats because you didnt select id as the first column

Angius•17mo ago

Meanwhile, in Dapper land

using (SqlConnection connection = new SqlConnection(connectionString))
            {
                var sql = "SELECT id, realname, nivel FROM Users WHERE  username = @username AND password = @password";

                    var loggedInUser = connection.QueryFirstOrDefault<UserData>(sql, new { username, password });

                if (loggedInUser != null)
                {
                    // open the main menu form
                    MainMenu mainMenu = new MainMenu(loggedInUser);
                    mainMenu.Show();
                    this.Hide();
                }
                else
                {
                    // invalid credentials, display error message
                    MessageBox.Show("Credenciais inválidas!");
                }
            }

using (SqlConnection connection = new SqlConnection(connectionString))
            {
                var sql = "SELECT id, realname, nivel FROM Users WHERE  username = @username AND password = @password";

                    var loggedInUser = connection.QueryFirstOrDefault<UserData>(sql, new { username, password });

                if (loggedInUser != null)
                {
                    // open the main menu form
                    MainMenu mainMenu = new MainMenu(loggedInUser);
                    mainMenu.Show();
                    this.Hide();
                }
                else
                {
                    // invalid credentials, display error message
                    MessageBox.Show("Credenciais inválidas!");
                }
            }

Accord•17mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ login system saves data from user