I am using backend SQL to access database for login details i.e., username and password but wihtout entering that it will logging in

private void button1_Click(object sender, EventArgs e)
       {
           SqlConnection con = new SqlConnection(@"Data Source=.;Database=master;Integrated Security=True");

           SqlDataAdapter sda = new SqlDataAdapter("SELECT * FROM Register WHERE usernmae='" + textBox1.Text + "' AND password='" + textBox2.Text + "'", con);
           /* in above line the program is selecting the whole data from table and the matching it with the user name and password provided by user. */
           con.Open();
           DataTable dt = new DataTable(); //this is creating a virtual table
           //sda.Fill(dt);
           con.Close();
           if (dt.Rows.Count >= 0)
           {
               /* I have made a new page called home page. If the user is successfully authenticated then the form will be moved to the next form */
               this.Hide();
               Dashboard  sn = new Dashboard();
               sn.Show();
               //new home().Show();
               //MessageBox.Show("done");
           }
           else
               MessageBox.Show("Not succesful Login");