private void button2_Click(object sender, EventArgs e)
        {
            web_interface form = new web_interface();

            form.Show();
            this.Close();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            string text1;
            string text2;
            bool   found = false;

            foreach (Credentials cred in credentials)
            {
                text1 = cred.username;
                text2 = cred.password;
                if (textBox1.Text == text1 && textBox2.Text == text2)
                {
                    found = true;
                    web_interface form2 = new web_interface();
                    File.WriteAllText(Application.StartupPath + "/loggedin.txt", textBox1.Text);
                    form2.Show();
                    this.Hide();
                }
            }

            if (!found)
            {
                MessageBox.Show("Ο συνδυασμός στοιχείων είναι λανθασμένος!");
            }
        }
        private void button2_Click(object sender, EventArgs e)
        {
            File.WriteAllText(Application.StartupPath + "/loggedin.txt", "");
            web_interface form = new web_interface();

            form.Show();
            this.Hide();
        }