BooksWindow.xaml

<Window x:Class="DatabaseExampleWPF.BooksWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Manage Books" 
        Height="600" 
        Width="900"
        WindowStartupLocation="CenterScreen">

    <!-- 
    This window demonstrates CRUD operations for the Books table
    Also shows many-to-many relationship management with Authors through BookAuthors table
    -->

    <Window.Resources>
        <!-- Button style for this window -->
        <Style TargetType="Button">
            <Setter Property="Padding" Value="10,5"/>
            <Setter Property="Margin" Value="5"/>
            <Setter Property="FontSize" Value="12"/>
            <Setter Property="Cursor" Value="Hand"/>
        </Style>

        <!-- TextBlock style -->
        <Style TargetType="TextBlock">
            <Setter Property="Margin" Value="5,5,5,2"/>
            <Setter Property="FontSize" Value="12"/>
        </Style>

        <!-- TextBox style -->
        <Style TargetType="TextBox">
            <Setter Property="Padding" Value="5"/>
            <Setter Property="Margin" Value="5,2,5,5"/>
            <Setter Property="FontSize" Value="12"/>
        </Style>
    </Window.Resources>

    <!-- 
    Main Grid with two columns:
    - Left: DataGrid showing all books
    - Right: Form for add/edit operations and author management
    -->
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <!-- Left column: takes proportional space -->
            <ColumnDefinition Width="350"/>
            <!-- Right column: fixed width for form -->
        </Grid.ColumnDefinitions>

        <!-- LEFT SIDE: Books List -->
        <Grid Grid.Column="0" Margin="10">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <!-- Header -->
                <RowDefinition Height="*"/>
                <!-- DataGrid -->
                <RowDefinition Height="Auto"/>
                <!-- Action buttons -->
            </Grid.RowDefinitions>

            <!-- Header -->
            <TextBlock Grid.Row="0" 
                       Text="Books List" 
                       FontSize="18" 
                       FontWeight="Bold"
                       Margin="5,5,5,10"/>

            <!-- 
            DataGrid: Displays data in a table format
            This is one of the most important WPF controls for displaying database records
            
            Properties explained:
            - x:Name: Name to reference in code
            - AutoGenerateColumns="False": We define columns manually for control
            - IsReadOnly="True": Users can't edit directly in grid
            - SelectionMode="Single": Only one row can be selected at a time
            - CanUserAddRows/DeleteRows="False": Disable inline add/delete
            - GridLinesVisibility: Show horizontal lines between rows
            - AlternatingRowBackground: Different color for every other row (easier to read)
            - SelectionChanged: Event when user selects a different row
            -->
            <DataGrid Grid.Row="1"
                      x:Name="dgBooks"
                      AutoGenerateColumns="False"
                      IsReadOnly="True"
                      SelectionMode="Single"
                      CanUserAddRows="False"
                      CanUserDeleteRows="False"
                      GridLinesVisibility="Horizontal"
                      AlternatingRowBackground="#F5F5F5"
                      SelectionChanged="DgBooks_SelectionChanged"
                      Margin="5">

                <!-- 
                DataGrid.Columns: Define what columns to display
                Each column is bound to a property of the Book object
                -->
                <DataGrid.Columns>
                    <!-- 
                    DataGridTextColumn: Displays text data
                    Binding: Specifies which property of the Book object to display
                    Header: Column header text
                    Width: Column width (Auto, *, or specific value)
                    -->
                    <DataGridTextColumn Header="ID" 
                                        Binding="{Binding BookID}" 
                                        Width="50"/>

                    <DataGridTextColumn Header="Title" 
                                        Binding="{Binding Title}" 
                                        Width="*"/>
                    <!-- Width="*" means take remaining space -->

                    <DataGridTextColumn Header="ISBN" 
                                        Binding="{Binding ISBN}" 
                                        Width="120"/>

                    <DataGridTextColumn Header="Year" 
                                        Binding="{Binding YearPublished}" 
                                        Width="70"/>
                </DataGrid.Columns>
            </DataGrid>

            <!-- Action Buttons -->
            <StackPanel Grid.Row="2" 
                        Orientation="Horizontal" 
                        HorizontalAlignment="Center"
                        Margin="5">
                <!-- Orientation="Horizontal": Stack buttons side by side -->

                <Button x:Name="btnRefresh"
                        Content="🔄 Refresh List"
                        Click="BtnRefresh_Click"
                        Background="#2196F3"
                        Foreground="White"/>

                <Button x:Name="btnDelete"
                        Content="🗑️ Delete Selected Book"
                        Click="BtnDelete_Click"
                        Background="#F44336"
                        Foreground="White"/>
            </StackPanel>
        </Grid>

        <!-- RIGHT SIDE: Add/Edit Form and Author Management -->
        <Grid Grid.Column="1" 
              Margin="10"
              Background="#F9F9F9">

            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <!-- Form header -->
                <RowDefinition Height="Auto"/>
                <!-- Book form -->
                <RowDefinition Height="*"/>
                <!-- Author management -->
            </Grid.RowDefinitions>

            <!-- Form Header -->
            <Border Grid.Row="0" 
                    Background="#1976D2" 
                    Padding="10"
                    Margin="0,0,0,10">
                <TextBlock x:Name="txtFormTitle"
                           Text="Add New Book" 
                           FontSize="16" 
                           FontWeight="Bold"
                           Foreground="White"
                           Margin="0"/>
            </Border>

            <!-- Book Entry Form -->
            <Border Grid.Row="1" 
                    Background="White" 
                    Padding="10"
                    Margin="0,0,0,10"
                    BorderBrush="#DDDDDD"
                    BorderThickness="1">

                <StackPanel>
                    <!-- 
                    Each field follows the pattern:
                    - Label (TextBlock)
                    - Input control (TextBox)
                    This is a standard form layout in WPF
                    -->

                    <TextBlock Text="Book Title *"/>
                    <TextBox x:Name="txtTitle"
                             MaxLength="200"/>
                    <!-- MaxLength: Limits how many characters can be entered -->

                    <TextBlock Text="ISBN"/>
                    <TextBox x:Name="txtISBN"
                             MaxLength="20"/>

                    <TextBlock Text="Year Published *"/>
                    <TextBox x:Name="txtYear"/>

                    <!-- Action Buttons -->
                    <StackPanel Orientation="Horizontal" 
                                HorizontalAlignment="Center"
                                Margin="0,15,0,0">

                        <Button x:Name="btnSave"
                                Content="💾 Save Book"
                                Click="BtnSave_Click"
                                Background="#4CAF50"
                                Foreground="White"
                                Width="110"/>

                        <Button x:Name="btnClear"
                                Content="🔄 Clear Form"
                                Click="BtnClear_Click"
                                Background="#FF9800"
                                Foreground="White"
                                Width="110"/>
                    </StackPanel>

                    <!-- Info text -->
                    <TextBlock Text="* Required fields"
                               FontSize="10"
                               FontStyle="Italic"
                               Foreground="Gray"
                               HorizontalAlignment="Center"
                               Margin="0,10,0,0"/>
                </StackPanel>
            </Border>

            <!-- Author Management Section -->
            <!-- 
            This section demonstrates managing the many-to-many relationship
            between Books and Authors through the BookAuthors junction table
            -->
            <Border Grid.Row="2" 
                    Background="White" 
                    Padding="10"
                    BorderBrush="#DDDDDD"
                    BorderThickness="1">

                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="Auto"/>
                    </Grid.RowDefinitions>

                    <!-- Section Header -->
                    <TextBlock Grid.Row="0"
                               Text="Manage Authors for Selected Book"
                               FontSize="14"
                               FontWeight="Bold"
                               Margin="5,5,5,10"/>

                    <!-- 
                    ListBox: Displays a list of items
                    Used here to show authors assigned to the selected book
                    -->
                    <ListBox Grid.Row="1"
                             x:Name="lstAssignedAuthors"
                             Margin="5"
                             MinHeight="100">
                        <!-- 
                        ItemTemplate: Defines how each item is displayed
                        DataTemplate: Template for the visual representation
                        -->
                        <ListBox.ItemTemplate>
                            <DataTemplate>
                                <!-- 
                                Binding to FullName property of Author object
                                Each item will display the author's full name
                                -->
                                <TextBlock Text="{Binding FullName}" 
                                           Margin="2"/>
                            </DataTemplate>
                        </ListBox.ItemTemplate>
                    </ListBox>

                    <!-- Add Author Section -->
                    <StackPanel Grid.Row="2" Margin="5,10,5,5">
                        <TextBlock Text="Add Author to Book:"/>

                        <!-- 
                        ComboBox: Dropdown list
                        Used to select an author to add to the book
                        DisplayMemberPath: Which property to show in dropdown
                        SelectedValuePath: Which property to use as the value
                        -->
                        <ComboBox x:Name="cboAvailableAuthors"
                                  DisplayMemberPath="FullName"
                                  SelectedValuePath="AuthorID"
                                  Margin="5,2,5,5"/>

                        <Button x:Name="btnAddAuthor"
                                Content="➕ Add Author to Book"
                                Click="BtnAddAuthor_Click"
                                Background="#4CAF50"
                                Foreground="White"
                                HorizontalAlignment="Stretch"/>
                    </StackPanel>

                    <!-- Remove Author Button -->
                    <Button Grid.Row="3"
                            x:Name="btnRemoveAuthor"
                            Content="➖ Remove Selected Author from Book"
                            Click="BtnRemoveAuthor_Click"
                            Background="#F44336"
                            Foreground="White"
                            Margin="5"
                            HorizontalAlignment="Stretch"/>

                    <!-- 
                    Note TextBlock - shown when no book is selected
                    This will be made visible/hidden in code-behind
                    -->
                    <TextBlock Grid.Row="0" Grid.RowSpan="4"
                               x:Name="txtNoBookSelected"
                               Text="Select a book from the list to manage its authors"
                               TextWrapping="Wrap"
                               VerticalAlignment="Center"
                               HorizontalAlignment="Center"
                               Foreground="Gray"
                               FontStyle="Italic"
                               Margin="20"/>
                </Grid>
            </Border>
        </Grid>
    </Grid>
</Window>