Chapter 7: Create Your Class Timetable Scheduler in .NET MAUI

using System.Collections.ObjectModel;
using System.Linq;
using TimetableScheduler.Models;
using TimetableScheduler.Services;

namespace TimetableScheduler
{
    public partial class MainPage : ContentPage
    {
        private readonly DatabaseService _dbService;

        public ObservableCollection<TimetableEntry> TimetableEntries { get; set; } = new();
        private List<TimetableEntry> AllEntries { get; set; } = new();

        public MainPage(DatabaseService dbService)
        {
            InitializeComponent();
            _dbService = dbService;
            BindingContext = this;

            LoadData();
        }

        private async void LoadData()
        {
            AllEntries = await _dbService.GetEntriesAsync();

            TimetableEntries.Clear();
            foreach (var entry in AllEntries)
                TimetableEntries.Add(entry);
        }

        private async void OnSaveClicked(object sender, EventArgs e)
        {
            if (string.IsNullOrWhiteSpace(subjectEntry.Text) ||
                string.IsNullOrWhiteSpace(teacherEntry.Text) ||
                string.IsNullOrWhiteSpace(timeEntry.Text) ||
                dayPicker.SelectedItem == null)
            {
                await DisplayAlert("Missing Info", "Please fill all fields.", "OK");
                return;
            }

            var entry = new TimetableEntry
            {
                Day = dayPicker.SelectedItem.ToString(),
                Subject = subjectEntry.Text.Trim(),
                Teacher = teacherEntry.Text.Trim(),
                Time = timeEntry.Text.Trim()
            };

            await _dbService.SaveEntryAsync(entry);

            subjectEntry.Text = string.Empty;
            teacherEntry.Text = string.Empty;
            timeEntry.Text = string.Empty;

            await LoadAndFilter(DayPicker.SelectedItem?.ToString());
            await DisplayAlert("Saved", "Timetable has been saved. Please select a day to view entries.", "OK");
        }

        private async void OnDeleteClicked(object sender, EventArgs e)
        {
            var button = sender as Button;
            var entry = button?.CommandParameter as TimetableEntry;

            if (entry != null)
            {
                await _dbService.DeleteTimetableEntryAsync(entry);
                AllEntries.Remove(entry);
                TimetableEntries.Remove(entry);
            }
        }

        private void OnDaySelected(object sender, EventArgs e)
        {
            if (DayPicker.SelectedItem is string selectedDay)
            {
                FilterByDay(selectedDay);
            }
        }

        private async Task LoadAndFilter(string selectedDay)
        {
            AllEntries = await _dbService.GetEntriesAsync();
            FilterByDay(selectedDay);
        }

        private void FilterByDay(string day)
        {
            var filtered = AllEntries
                .Where(e => e.Day.Equals(day, StringComparison.OrdinalIgnoreCase))
                .ToList();

            TimetableEntries.Clear();
            foreach (var item in filtered)
                TimetableEntries.Add(item);
        }
    }
}

using System;
using System.IO;
using Microsoft.Maui.Storage; // Needed for FileSystem.AppDataDirectory
using TimetableScheduler.Services; // ✅ This fixes the 'DatabaseService' not found
using TimetableScheduler;

namespace TimetableScheduler
{
    public partial class App : Application
    {
        public static string DatabasePath { get; private set; }

        public App()
        {
            InitializeComponent();

            // ✅ Set database path in a writable location
            DatabasePath = Path.Combine(
                FileSystem.AppDataDirectory, "timetable.db");

            // ✅ Initialize DatabaseService with path
            var databaseService = new DatabaseService(DatabasePath);

            // ✅ Pass the DatabaseService to MainPage
            MainPage = new NavigationPage(new MainPage(databaseService));
        }
    }
}
    

using Microsoft.Extensions.Logging;
using TimetableScheduler.Services; // <-- Required for DatabaseService
using System.IO;

namespace TimetableScheduler
{
    public static class MauiProgram
    {
        public static MauiApp CreateMauiApp()
        {
            var builder = MauiApp.CreateBuilder();

            builder
                .UseMauiApp<App>()
                .ConfigureFonts(fonts =>
                {
                    fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                    fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
                });

#if DEBUG
            builder.Logging.AddDebug();
#endif

            // ✅ Register DatabaseService as a singleton
            string dbPath = Path.Combine(FileSystem.AppDataDirectory, "timetable.db3");
            builder.Services.AddSingleton(new DatabaseService(dbPath));

            // ✅ Register MainPage so it can be injected into App.xaml.cs
            builder.Services.AddSingleton<MainPage>();

            return builder.Build();
        }
    }
}