ASP.NET Login in n-tier architecture

Question

I'm trying to implement login functionality in ASP.NET C# based on n-tier architecture.

Data access:

public int userlogin(string user, string passw)//checking the user name and password
{
    SqlConnection con = new SqlConnection();
    con.ConnectionString = GetConnectionString();
    con.Open();
    int id = 0;
    string selectstr = "SELECT NurseName, password FROM Nurse2 WHERE NurseName = '" + user.Trim() + "' AND Password = '" + passw.Trim() + "'";
    SqlCommand cmd = new SqlCommand();
    cmd.CommandText = selectstr;
    cmd.CommandType = System.Data.CommandType.Text;
    cmd.Connection = con;
    SqlDataReader reader = cmd.ExecuteReader();
    while (reader.Read())
    {
        id++;
    }
    cmd = null;
    reader.Close();
    con.Close();
    return id;
}

Presentation layer .cs file

protected void Button1_Click(object sender, EventArgs e)
{
    string name = TextBox1.Text;
      string password = TextBox2.Text;
    int id = da.userlogin(name, password);
    if (id > 0)
    {
        Session["userName"] = name;

        Response.Redirect("SubscribePage.aspx");

    }
    else
    {
        Label1.Text = "invalid";
    }

Now, my issue is when I press button the program simply goes to else clause, even though I enter correct data. What could be possibly not OK here as to me it all seems fine.

Answer 1

I don't think you need to do that nowadays. ASP.NET has built-in authentication. Just check this out https://msdn.microsoft.com/en-us/library/xdt4thhy(v=vs.140).aspx .

Answer 2

The N-Tier architecture helps separate your code, as it is your code is jumping a layer and does not fully utilizing the business logic layer. Here is a helpful image;

I would also add an additional class to store your users login details, I'm guessing you will have more information along with the nurse name to store - You can store the instance of this class in your session data and cast it out when needed;

public class User
{
    public string Name        { get; set; }
    /* Some other attributes - not your password though! */
}

--

Presentation;

    protected void Button1_Click(object sender, EventArgs e)
    {
        try
        {
            Session["User"] = BLL.userLogin(TextBox1.Text, TextBox2.Text);
            Response.Redirect("SubscribePage.aspx"); /* If it reaches here, everything is okay */
        }
        catch (Exception ex)
        {
            Label1.Text = ex.Message;
        }
    }

Business Layer;

    public static User userLogin(string username, string password)
    {
        User U = DAL.userLogin(username, password);

        if (string.IsNullOrEmpty(U.Name))
            throw new Exception("Incorrect login details");

        return U;
    }

Data Access Layer;

    public static User userLogin(string username, string password)
    {
        using (SqlConnection con = new SqlConnection(GetConnectionString())
        {
            User U = new User();

            SqlCommand cmd = new SqlCommand(@"SELECT NurseName, password 
                                                FROM Nurse2 
                                                WHERE NurseName = @user AND password = @pw", con);

            cmd.Parameters.Add(new SqlParameter("@user", username));
            cmd.Parameters.Add(new SqlParameter("@pw", password));

            try
            {
                con.Open();
            }
            catch (Exception ex)
            {
                throw new Exception("connetion problem", ex);
            }

            try
            {
                using (SqlDataReader rdr = cmd.ExecuteReader())
                {
                    while (rdr.Read())
                    {
                        U = rdr["NurseName"];
                    }
                }
            }
            catch (Exception ex)
            {
                throw new Exception("problem with query", ex);
            }
            finally
            {
                con.Close(); /* Clean up regardless of the outcome */
                con.Dispose();
            }

            return U;
        }
    }

Have a read up more into the N-Tier architecture, and try-catch statements. Hope it helps. I would also improve your naming conventions for your controls, to make life easier (ie Label1 -> lblError)