private void btnLogin_Click(object sender, EventArgs e)
        {
            var db = new DataModels.FundRaiserEntities();

            var md5 = System.Security.Cryptography.MD5CryptoServiceProvider.Create();
            byte[] hashedPassword = md5.ComputeHash(System.Text.Encoding.UTF8.GetBytes(txtPassword.Text));


            var manager = (from m in db.Manager
                          where m.Username == txtUsername.Text
                                && m.PasswordHash == hashedPassword
                                && m.SuperManager == true
                          select m).SingleOrDefault();

            if (manager == null)
            {
                MessageBox.Show("Invalid username or password.", "Fundraiser Login", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1);
                txtUsername.Focus();
                return;
            }

            // todo: load the main form and close this form.
        }