public Form1()
        {
            InitializeComponent();
        }
        string[] names = new string[2];

        string[] ussernames = { "ussername1", "ussername2" };
        string[] passwords = { "password1", "password2" };
        int i = 0;


        private void button1_Click(object sender, EventArgs e)
        {
            if (ussernames.Contains(textBox1.Text) && passwords.Contains(textBox2.Text) && Array.IndexOf(ussernames, textBox1.Text) == Array.IndexOf(passwords, textBox2.Text))
            {
                Form2 f2 = new Form2();
                f2.ShowDialog();
            }
            else
                MessageBox.Show("The username or password is incorrect");
        }

        private void button2_Click(object sender, EventArgs e)
        {
            for (i = 0; i < names.Length; i = i++)
            {
                textBox1.Text += names[i];
            }

        }
    }
}