protected void btnSubmit_Click(object sender, EventArgs e)
    {
        string FirstName = txtFirstName.Text;
        string LastName = txtLastName.Text;
        string Username = txtUsername.Text;
        int BirthYear = int.Parse(txtDate.Text);
        string Password = txtPassword.Text;
        string ValidatePassword = txtPassword1.Text;
        string Countries = txtCountries.Text;

        string sql = "SELECT * FROM Register WHERE Username=" + Username;
        string con = "Data Source=(LocalDB)\\MSSQLLocalDB;";
        con += "AttachDbFilename =|DataDirectory|\\Database.mdf;";
        con += "Integrated Security=True;";

        SqlConnection connection = new SqlConnection(con);
        connection.Open();
        SqlCommand command = new SqlCommand(sql, connection);
        SqlDataReader reader = command.ExecuteReader();
        if (!reader.HasRows)
        {
            reader.Close();
            sql = "INSERT INTO Register(FirstName, LastName, Uesrname, BirthYear, Password, ValidatePassword) ";
            sql += string.Format("VALUES({0}, '{1}', '{2}', '{3}', {4}, {5}, {6}')", FirstName, LastName, Username, BirthYear, Password, ValidatePassword, Countries);
            command = new SqlCommand(sql, connection);
            command.ExecuteNonQuery();
        }
        else
        {
            lblError.Text = "User already exists";
        }