How do I solve this? System.data.oledb.oledbexception: 'syntax error (missing operator) in query expression ''varga, '02134')'.'

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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.OleDb;

namespace Gyakorlás1111
{
    public partial class frmRegister : Form
    {
        public frmRegister()
        {
            InitializeComponent();

           
        }
        OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=db_users.mdb");
        OleDbCommand cmd = new OleDbCommand();
        OleDbDataAdapter da = new OleDbDataAdapter();

        private void button1_Click(object sender, EventArgs e)
        {
            if (txtUsername.Text == "" && txtPassword.Text == "" && txtComPassword.Text == "")
            {
                MessageBox.Show("Username and Password fuelds are empty", "Registration Faield", MessageBoxButtons.OK, MessageBoxIcon.Error);

            }
            else if (txtPassword.Text == txtComPassword.Text)
            {
                con.Open();
                string register = "INSERT INTO tbl_users  VALUES ('"+txtUsername.Text+",'"+txtPassword.Text+"')";
                cmd = new OleDbCommand(register, con);
                cmd.ExecuteNonQuery();
                con.Close();

                txtUsername.Text = "";
                txtPassword.Text = "";
                txtComPassword.Text = "";

                MessageBox.Show("Your Account has been Successfully Created", "Registration Success", MessageBoxButtons.OK, MessageBoxIcon.Information);


            }
            else
            {
                MessageBox.Show("Passwords does not match, Please Re-enter", "Registartion Faield", MessageBoxButtons.OK, MessageBoxIcon.Error);
                txtPassword.Text = " ";
                txtComPassword.Text = " ";
                txtPassword.Focus();
            }
        }

        private void checkBox1_CheckedChanged(object sender, EventArgs e)
        {
            if (checkbxShowPass.Checked)
            {
                txtPassword.PasswordChar = '\0';
                txtComPassword.PasswordChar = '\0';
            }
            else
            {
                txtPassword.PasswordChar = '•';
                txtComPassword.PasswordChar = '•';
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            txtUsername.Text = "";
            txtPassword.Text = "";
            txtComPassword.Text = "";
            txtUsername.Focus();
        }

        private void label5_Click(object sender, EventArgs e)
        {
            new frmLogin().Show();
            this.Hide();
        }
    }
}

What I have tried:

I'm new to this stuff so not sure what to try..

Posted 17-Nov-22 11:24am

Varga Gergő (Gergő)

Updated 17-Nov-22 11:33am

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OriginalGriff · Accepted Answer · 2022-11-17T11:33:00

Simple: your quotes don't match up.

But ... you have much, much bigger problems that you need to address throughout your app as a matter of urgency.

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?

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.