private void btnLogin_Click(object sender, EventArgs e)
        {
            string username = "m";
            string password = "k";
            bool check = true;
            for (int i = 0; i < current; i++)
            {
                if (reg[i].username == txtUsername.Text && reg[i].password == txtPassword.Text)
                {
                    MessageBox.Show("Login Successful!", "Successful", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                    gbRegister.Enabled = false;
                    gbConversion.Enabled = true;
                    disableLogin();

                    txtFname.Clear();
                    txtLname.Clear();
                    txtRusername.Clear();
                    txtRpassword.Clear();

                    txtUsername.Clear();
                    txtPassword.Clear();
                    check = false;
                }

            }



                if (txtUsername.Text == username && txtPassword.Text == password && check==true)
                {
                    MessageBox.Show("Login Successful!", "Successful", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);

                    gbRegister.Enabled = false;
                    gbConversion.Enabled = true;
                    disableLogin();


                    txtUsername.Clear();
                    txtPassword.Clear();
                }


                else if(check== true)
                {
                    MessageBox.Show("Invalid Username or Password");
                    txtUsername.Clear();
                    txtPassword.Clear();
                }

        }