SqlDataAdapter sda = new SqlDataAdapter("Select Count(*) From Login where USERNAME ='" + txtUsername.Text + "' and PASSWORD ='" + txtPassword.Text + "'",con);
        DataTable dt = new DataTable();
        sda.Fill(dt);
            if (dt.Rows[0][0].ToString() == "1")
                {
                    this.Hide();
                    CTMain ss = new CTMain();
                    ss.Show();
                }
            else
                {
                    MessageBox.Show("Please check your Username and/or Password");
                }

private void CTMain_Load(object sender, EventArgs e)

    {
        cbxListstores.Items.Clear();
        con.Open();
        SqlCommand scm = con.CreateCommand();
        scm.CommandType = CommandType.Text;
        scm.CommandText = "select STORENAME from Login";
        scm.ExecuteNonQuery();
        DataTable dt = new DataTable();
        SqlDataAdapter sda = new SqlDataAdapter(scm);
        sda.Fill(dt);
        foreach (DataRow dr in dt.Rows)
            {
                cbxListstores.Items.Add(dr["STORENAME"].ToString());
                cbxListstores.SelectedIndex = 0;
            }
        con.Close();
    }