login page for c# and mysql database

 i am currently trying to design a login page... but looks like i have a problem...  i would appreciate if mistakes are pointed out...
my codes are as follows
    private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                DataSet1 dat = new DataSet1();
                DataSet1TableAdapters.usersTableAdapter usr2 = new DataSet1TableAdapters.usersTableAdapter();
                usr2.FillBy(dat.users, textBox1.Text, textBox3.Text);
                string usrnm = dat.users.Rows[0][0].ToString();
                string mode = dat.users.Rows[0][1].ToString();
                string passwrd = dat.users.Rows[0][2].ToString();
                if (usrnm == textBox1.Text && passwrd == textBox3.Text)
                {
                    if (mode == "IndustryMode")
                    {
                    IndustryModePage ind = new IndustryModePage();
                    ind.MdiParent = this;
                    ind.Show();
                    }
                    else if (mode == "HomeMode")
                    {
                        HomeModePage hom = new HomeModePage();
                        hom.MdiParent = this;
                        hom.Show();  }
                }
                else
                {
                    MessageBox.Show("wrong user/password combination");
                }
            }
            catch
            {
                MessageBox.Show("non existing user");
            }
        }
    }
its giving me an error that even my existing users are non existing.