How do I open two different based on user rights?

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I developed an application with sql server database. I have table for user login with admin and normal user. The problem when I login with normal user it open the form for Admin as well as for normal user. In short it opens two forms when I login with normal user. Please assist.

What I have tried:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Stokvel_Management_System
{
    public partial class Login : Form
    {
        public Login()
        {
            InitializeComponent();
        }
        public string constring = "Data Source=LAPTOP-TINYIKOB\\SQLEXPRESS;Initial Catalog=Stokvel;Integrated Security=True";
                         
        private void BtnLogin_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(constring);
            con.Open();
            
            SqlDataAdapter da = new SqlDataAdapter("select count(*) from loginTab where UserName='" + txtUsername.Text + "' and Password='" + txtPassword.Text + "'and Type='" + UsercomboBox.Text + "'", con);
            DataTable dt = new DataTable();
            da.Fill(dt);
            if (dt.Rows[0][0].ToString() == "1")
            {
                SqlDataAdapter da1 = new SqlDataAdapter("select Type from loginTab where UserName='" + txtUsername.Text + "' and Password='" + txtPassword.Text  + "'", con);
                DataTable dt1 = new DataTable();
                da1.Fill(dt1);
                if (dt1.Rows[0][0].ToString() == "Admin")
                    con.Close();
                {
                    Hide();
                    Admin ad = new Admin();
                    ad.Show();
                }
                if(dt1.Rows[0][0].ToString()=="User")
                {
                    Hide();
                    User us = new User();
                    us.Show();
                    
                }
            }

            
            }

        }
    }

Posted 2-Mar-24 6:29am

NyikoB

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2 solutions

Solution 1

You have worst problems to deal with first, so I'll explain what you have noticed last.

1) Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

And on a LOGIN SCREEN? That's positively suicidal as I don't even have to be a user to destroy your DB!

2) Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]

And remember: if you have any European Union users then GDPR applies and that means you need to handle passwords as sensitive data and store them in a safe and secure manner. Text is neither of those and the fines can be .... um ... outstanding. In December 2018 a German company received a relatively low fine of €20,000 for just that.

3) You don't check if the DB returned any rows: if you mistype, it will throw an "index out of range" error and your app will crash.

4) You only close the connection for Admins. Instead on manually closing the connection, surround the whole DB code in using blocks and the system will automatically tidy up for you.

5) The problem you have noticed ... Look at your code:

if (dt1.Rows[0][0].ToString() == "Admin")
    con.Close();
{
    Hide();
    Admin ad = new Admin();
    ad.Show();
}

If the condition matches it closes the connection.Then it always executes the code in the curly brackets even if the condition didn't match ...

Posted 2-Mar-24 6:39am

OriginalGriff

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Richard MacCutchan · Accepted Answer · 2024-03-02T06:50:00

That looks excessively complex to me. All you really need is to read the row that matches the given username and password, and returns the user type. With that information you can then open either the admin or the user form. Creating two dataadapters and datatables just to read a single row is somewhat wasteful of resources. Something like:

C#

string queryString = "select Type from loginTab where UserName='" + txtUsername.Text + "' and Password='" + txtPassword.Text  + "'";
string usertype = "None";
using (SqlConnection connection = new SqlConnection(
           connectionString))
{
    SqlCommand command = new SqlCommand(
        queryString, connection);
    connection.Open();
    using(SqlDataReader reader = command.ExecuteReader())
    {
        while (reader.Read())
        {
            usertype = reader[0]; // returned value
        }
    }
}
if (usertype == "Admin")
{
    Hide();
    Admin ad = new Admin();
    ad.Show();
}
else if(usertype == "User")
{
    Hide();
    User us = new User();
    us.Show();   
}
else
{
    // invalid type, or no matching record.
}