Data/BookRepository.cs:
`
using BookViewer.Model;
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BookViewer.Data
{
    public class BookRepository
    {
        private SqlConnection _connection;

        public BookRepository()
        {
            _connection = new SqlConnection(Properties.Settings.Default.connectionstring);
        }

        public List<Book> GetBooks()
        {
            List<Book> books = new List<Book>();

            _connection.Open();
            using (SqlCommand command = new SqlCommand("SELECT * FROM Books;", _connection))
            {
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        books.Add(new Book(
                            (string)reader["Id"],
                            (string)reader["Author"],
                            (string)reader["Title"],
                            (string)reader["Genre"],
                            (double)reader["Price"],
                            (DateTime)reader["PublishDate"],
                            (string)reader["Description"]
                        ));
                    }
                }
            }
            _connection.Close();
            return books;
        }

        public void UpdateBook(Book book)
        {
            _connection.Open();
            string query = @"UPDATE Books SET Author = @Author, Title = @Title WHERE Id = @Id;";
            using (SqlCommand command = new SqlCommand(query, _connection))
            {
                command.Parameters.AddWithValue("@Author", book.Author);
                command.Parameters.AddWithValue("@Title", book.Title);
                command.Parameters.AddWithValue("@Id", book.Id);

                command.ExecuteNonQuery();
            }


            _connection.Close();
        }

        public void InsertBook(Book book)
        {
            _connection.Open();

            string query = "INSERT INTO Books (Id, Author, Title, Genre, Price, PublishDate, Description) VALUES (@Id, @Author, @Title, @Genre, @Price, @PublishDate, @Description);";
            using (SqlCommand command = new SqlCommand(query, _connection))
            {
                command.Parameters.AddWithValue("@Id", book.Id);
                command.Parameters.AddWithValue("@Author", book.Author);
                command.Parameters.AddWithValue("@Title", book.Title);
                command.Parameters.AddWithValue("@Genre", book.Genre);
                command.Parameters.AddWithValue("@Price", book.Price);
                command.Parameters.AddWithValue("@PublishDate", book.PublishDate);
                command.Parameters.AddWithValue("@Description", book.Description);

                command.ExecuteNonQuery();
            }

            _connection.Close();
        }
    }
}
`
--------------------------------------------------------------------------------------------------------------
Model/Book.cs:
`
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BookViewer.Model
{
    public class Book
    {
        public string Id { get; set; }
        public string Author { get; set; }
        public string Title { get; set; }
        
        public string Genre { get; set; }

        public double Price { get; set; }
        public DateTime PublishDate { get; set; }
        public string Description { get; set; }

        public Book(string id, string author, string title, string genre, double price, DateTime publishDate, string description)
        {
            Id = id;
            Author = author;
            Title = title;
            Genre = genre;
            Price = price;
            PublishDate = publishDate;
            Description = description;
        }

        public override string ToString()
        {
            return this.Title;
        }
    }
}
`
-----------------------------------------------------------------------------------------------------------------
ViewModel/BookCatalougePageViewModel.cs:
`
using BookViewer.Data;
using BookViewer.Model;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BookViewer.ViewModel
{
    public class BookCatalougePageViewModel
    {
        private BookRepository _repository;
        public ObservableCollection<Book> Books { get; set; }
        public Book SelectedBook { get; set; }
        public string NewTitle { get; set; }
        public string NewAuthor { get; set; }
        public string NewDescription { get; set; }
        public DateTime NewPublishDate { get; set; }
        public string NewId { get; set; }
        public double? NewPrice { get; set; }
        public string NewGenre { get; set; }


        public BookCatalougePageViewModel(BookRepository repository)
        {
            _repository = repository;
            Books = new ObservableCollection<Book>(_repository.GetBooks());
        }

        public void UpdateBook(Book book)
        {
            

            if (book == null) return;
            _repository.UpdateBook(book);
            
        }

        public void InsertBook(Book book)
        {
            _repository.InsertBook(book);
            Books.Add(book);
        }
        
    }
}
`
---------------------------------------------------------------------------------------------------------
ViewModel/BookDetailsPageViewModel.cs
`
using BookViewer.Data;
using BookViewer.Model;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BookViewer.ViewModel
{
    public class BookDetailsPageViewModel
    {
        private BookRepository _repository;
        public Book Book {  get; }

        public BookDetailsPageViewModel(BookRepository repository, Book book)
        {
            _repository = repository;
            Book = book;
        }
    }
}
`
-----------------------------------------------------------------------------------------------------------------
xaml and xaml.cs files:
App.xaml and App.xaml.cs:

`
<Application x:Class="BookViewer.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:BookViewer"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <Style x:Key="headerStyle">
            <Setter Property="Label.FontSize" Value="20"/>
            <Setter Property="Label.FontWeight" Value="Bold"/>
            <Setter Property="Label.Foreground" Value="Black"/>
        </Style>
    </Application.Resources>
</Application>
-----------------------------------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;

namespace BookViewer
{
    /// <summary>
    /// Interaktionslogik für "App.xaml"
    /// </summary>
    public partial class App : Application
    {

    }
}
`
---------------------------------------------------------------------------------------------
BookCatalougePage.xaml and .xaml.cs:
`
<Page x:Class="BookViewer.BookCatalougePage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:BookViewer"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="BookCatalougePage">

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="50px"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <Label Style="{ StaticResource headerStyle}" Grid.Row="0" Grid.Column="0" >
            Book Catalouge
        </Label>
        <DataGrid Grid.Row="1" Grid.Column="0" ItemsSource="{ Binding Books, Mode=TwoWay}" SelectedItem="{ Binding SelectedBook, Mode=TwoWay }" AutoGenerateColumns="False" VerticalAlignment="Top" CellEditEnding="DataGrid_CellEditEnding">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Title"  Binding="{Binding Title}" Width="2*"/>
                <DataGridTextColumn Header="Author" Binding="{Binding Author}" Width="*"/>
            </DataGrid.Columns>
        </DataGrid>

        

        <StackPanel Grid.Row="1" Grid.Column="1" VerticalAlignment="Top">
            <Button Name="View_Button" Click="View_Button_Click"  Grid.Row="1" Grid.Column="1" Margin="10, 10, 10, 10" Height="35px" Width="Auto">
                View Details
            </Button>
            <TextBox TextWrapping="Wrap" Name="NewId_Input" Text="{Binding NewId, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="20px" Margin="10,10,0,10"/>
            <TextBox TextWrapping="Wrap" Name="NewTitle_Input" Text="{Binding NewTitle, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="20px" Margin="10,10,0,10"/>
            <TextBox TextWrapping="Wrap" Name="NewAuthor_Input" Text="{Binding NewAuthor, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="20px" Margin="10,10,0,10"/>
            <TextBox TextWrapping="Wrap" Name="NewGenre_Input" Text="{Binding NewGenre, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="20px" Margin="10,10,0,10"/>
            <TextBox TextWrapping="Wrap" Name="NewPrice_Input" Text="{Binding NewPrice, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="20px" Margin="10,10,0,10"/>
            <TextBox TextWrapping="Wrap" Name="NewPublishDate_Input" Text="{Binding NewPublishDate, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="20px" Margin="10,10,0,10"/>
            <TextBox AcceptsReturn="True" TextWrapping="Wrap" Name="NewDescription_Input" Text="{Binding NewDescription, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, TargetNullValue=''}" Height="100px" Margin="10,10,0,10"/>
            <Button Name="Add_Book_Button" Click="Add_Book_Button_Click" Height="30px" Margin="10, 10, 10, 0">
                Add Book
            </Button>
        </StackPanel>
    </Grid>
</Page>
-------------------------------------------------------------------------------------------------------------------------------------------------------
using BookViewer.Data;
using BookViewer.ViewModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using BookViewer.Model;

namespace BookViewer
{
    /// <summary>
    /// Interaktionslogik für BookCatalougePage.xaml
    /// </summary>
    public partial class BookCatalougePage : Page
    {
        private BookRepository _repository;
        private BookCatalougePageViewModel _viewModel;
        public BookCatalougePage()
        {
            _repository = new BookRepository();
            _viewModel = new BookCatalougePageViewModel(_repository);
            InitializeComponent();
            this.DataContext = _viewModel;
        }

        private void View_Button_Click(object sender, RoutedEventArgs e)
        {
            if (_viewModel.SelectedBook == null) return;

            NavigationService.Navigate(new BookDetailsPage(_repository, _viewModel.SelectedBook));
        }

        private void DataGrid_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
        {
            e.EditingElement.GetBindingExpression(TextBox.TextProperty)?.UpdateSource();

            

            this._viewModel.UpdateBook((Book)e.Row.Item);
        }

        private void Add_Book_Button_Click(object sender, RoutedEventArgs e)
        {
            if (_viewModel.NewId  == null || _viewModel.NewAuthor == null 
                || _viewModel.NewTitle == null || _viewModel.NewGenre == null || _viewModel.NewPrice == null
                || _viewModel.NewPublishDate == null || _viewModel.NewDescription == null || _viewModel.NewPublishDate.Year < 1753)
            {
                MessageBox.Show("Please Enter valid values in each field");
                return;
            }

            Book newBook = new Book(
                _viewModel.NewId,
                _viewModel.NewAuthor,
                _viewModel.NewTitle,
                _viewModel.NewGenre,
                (double) _viewModel.NewPrice,
                _viewModel.NewPublishDate,
                _viewModel.NewDescription
            );

            _viewModel.InsertBook(newBook);
        }
    }
}
`
------------------------------------------------------------------------------------------------------------
BookDetailsPage.xaml and .xaml.cs:
`
<Page x:Class="BookViewer.BookDetailsPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:BookViewer"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="BookDetailsPage">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height ="70px"/>
            <RowDefinition/>
        </Grid.RowDefinitions>


        <Label Grid.Row="0" Margin="10, 10, 0, 10" Style="{StaticResource headerStyle }">
            <TextBlock >
                <Run Text="Book Details for: "/>
                <Run Text="{ Binding Book.Title }"/>
            </TextBlock>

        </Label>
        <StackPanel Grid.Row="1" DataContext="{Binding Book}">
            <Border Height="40px">
                <TextBlock>
                    <Run Text="Author: "/>
                    <Run Text="{Binding Author}"/>
                </TextBlock>
            </Border>
            <Border Height="40px">
                <TextBlock>
                    <Run Text="Genre: "/>
                    <Run Text="{Binding Genre}"/>
                </TextBlock>
            </Border>
            <Border Height="40px">
                <TextBlock>
                    <Run Text=" Price: "/>
                    <Run Text="{Binding Price}"/>
                </TextBlock>
            </Border>
            <Border Height="40px">
                <TextBlock>
                    <Run Text="Publish Date: "/>
                    <Run Text="{Binding PublishDate}"/>
                </TextBlock>
            </Border>
            <Border Height="40px">
                <TextBlock>
                <Run Text="Description: "/>
                <Run Text="{Binding Description}"/>
                </TextBlock>
            </Border>

        </StackPanel>

    </Grid>
</Page>
-----------------------------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using BookViewer.Data;
using BookViewer.Model;
using BookViewer.ViewModel;

namespace BookViewer
{
    /// <summary>
    /// Interaktionslogik für BookDetailsPage.xaml
    /// </summary>
    public partial class BookDetailsPage : Page
    {
        private BookDetailsPageViewModel _viewModel;

        public BookDetailsPage(BookRepository _repository, Book selectedBook)
        {
            this._viewModel = new BookDetailsPageViewModel(_repository, selectedBook);
            InitializeComponent();
            this.DataContext = _viewModel;
        }
    }
}
`