SqlCommand cmd = conn.CreateCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "select * from Loginform where username='" + metroTextBox1.Text + "' and password='" + metroTextBox2.Text + "'";
        cmd.ExecuteNonQuery();
        DataTable dt = new DataTable();
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        da.Fill(dt);
        i = Convert.ToInt32(dt.Rows.Count.ToString());
        if (i == 0)
        {
            //conn.Close();
            MessageBox.Show("Вы ввели неверный логин или пароль");

        }
        else
        {

            this.Hide();
            LENTA f = new LENTA();
            f.Show();
        }

if (username.Text == "" || pass.Text == "")
            MessageBox.Show("please fill all fields");
        else if (pass.Text != conpass.Text)
            MessageBox.Show("password do not match");
        else
        {
            using (conn)
            {
                SqlCommand cmd = new SqlCommand("UserAdd", conn);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("Id", metroTextBox3.Text.Trim());
                cmd.Parameters.AddWithValue("Firstname", name.Text.Trim());
                cmd.Parameters.AddWithValue("Surname", surname.Text.Trim());
                cmd.Parameters.AddWithValue("Telnumber", tel.Text.Trim());
                cmd.Parameters.AddWithValue("Username", username.Text.Trim());
                cmd.Parameters.AddWithValue("Password", pass.Text.Trim());

                    cmd.ExecuteNonQuery();
                MessageBox.Show("registration is successfull");
                Clear();
            }
        }