private void Login()
{
if (Authenticate(tb_User.Text, tb_Password.Text))
{
this.Hide();
ClientHandler clientHandler = new ClientHandler();
clientHandler.Show();
}
else
{
tb_User.Focus();
tb_User.SelectAll();
MessageBox.Show("Username or Password not invalid!", "Authentication failure", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}