Hotel Reservations

using System;
using System.Windows.Forms;

namespace Reservations
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        public bool IsValidData()
        {
            return

                IsPresent(txtArrivalDate, "Arrival Date") &&
                IsDateTime(txtArrivalDate, "Arrival Date") &&
                IsWithinRange(txtArrivalDate, "Arrival Date", DateTime.Today, DateTime.Today.AddYears(5)) &&

                IsPresent(txtDepartureDate, "Departure Date") &&
                IsDateTime(txtDepartureDate, "Departure Date") &&
                IsWithinRange(txtDepartureDate, "Departure Date", DateTime.Today, DateTime.Today.AddYears(5));
        }

        public bool IsPresent(TextBox textBox, string name)
        {
            if (textBox.Text == "")
            {
                MessageBox.Show(name + " is a required field.", "Entry Error");
                textBox.Focus();
                return false;
            }
            return true;
        }

        public bool IsDateTime(TextBox textBox, string name)
        {
            if (DateTime.TryParse(textBox.Text, out DateTime dt))
            {
                return true;
            }
            else
            {
                MessageBox.Show(name + " is not valid ", "ENTRY ERROR");
                return false;
            }
        }

        public bool IsWithinRange(TextBox textBox, string name,
            DateTime min, DateTime max)
        {
            DateTime dt = DateTime.Parse(textBox.Text);

            if (dt < min || dt > max)
            {
                MessageBox.Show(name + " must be between " + min + " and " + max + " .", "ENTRY ERROR");
                textBox.Focus();
                return false;
            }
            return true;
        }

        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnCalculate_Click(object sender, EventArgs e)
        {
            try
            {
                if (IsValidData())
                {
                    DateTime arrDate = Convert.ToDateTime(txtArrivalDate.Text);
                    DateTime depDate = Convert.ToDateTime(txtDepartureDate.Text);

                    if (arrDate >= depDate)
                    {
                        MessageBox.Show("Departure date should be after the arrival date");
                    }
                    else
                    {
                        double price_perNight = 0;
                        double total = 0;
                        double average;
                        DateTime arrivalDate = DateTime.Today;
                        DateTime.TryParse(txtArrivalDate.Text, out arrivalDate);
                        DateTime departureDate = DateTime.Today;
                        DateTime.TryParse(txtDepartureDate.Text, out departureDate);
                        TimeSpan totalTime = departureDate.Subtract(arrivalDate);
                        int totalNights = totalTime.Days;
                        txtNights.Text = totalNights.ToString();

                        DayOfWeek dayOfWeek = arrivalDate.DayOfWeek;

                        for (DateTime counter = DateTime.Now; counter < departureDate; counter = counter.AddDays(1))
                        {
                            if (counter.DayOfWeek == DayOfWeek.Friday || counter.DayOfWeek == DayOfWeek.Saturday)
                            {
                                price_perNight = 150;
                            }
                            else
                            {
                                price_perNight = 120;
                            }
                            total += price_perNight;
                        }
                        txtTotalPrice.Text = total.ToString("c");
                        average = total / totalNights;
                        txtAvgPrice.Text = average.ToString("c");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message + "\r\n" + ex.StackTrace + "\r\n" + ex.GetType().ToString(),
                    "EXCEPTION");
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            DateTime currentDate = DateTime.Today;
            DateTime depDate = currentDate.AddDays(3);
            txtArrivalDate.Text = currentDate.ToShortDateString().Replace("-", "/");
            txtDepartureDate.Text = depDate.ToShortDateString().Replace("-", "/");


        }
    }
}