UserControl designed as modal presenter for the main window #wpf #csharp

ModalPresenterControl.xaml

<UserControl ...>
  <UserControl.Resources>
        <c:NullToVisibilityConverter x:Key="NullToVisibilityConverter" />
        <c:NullToBoolConverter x:Key="NullToBoolConverter" />
        <Style x:Key="ModalVisibility" TargetType="FrameworkElement">
            <Setter Property="Visibility" Value="Collapsed" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding ModalToShow, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}, Converter={StaticResource NullToBoolConverter}}" Value="True">
                    <Setter Property="Visibility" Value="Visible" />
                </DataTrigger>
                <DataTrigger Binding="{Binding ModalToShow, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}, Converter={StaticResource NullToBoolConverter}}" Value="False">
                    <Setter Property="Visibility" Value="Collapsed" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </UserControl.Resources>
    <Grid>
        <ContentControl>
            <ContentPresenter Content="{Binding ViewToShow, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"/>
        </ContentControl>
        <!-- The Rectangle is what simulates the modality -->
        <Rectangle x:Name="Overlay" Opacity="0.4" Fill="LightGray" Style="{StaticResource ModalVisibility}" />
        <Grid x:Name="Dialog" Style="{StaticResource ModalVisibility}">
            <!-- The template for the dialog goes here (borders and such...) -->
            <ContentPresenter x:Name="Modal" Content="{Binding ModalToShow, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}" />
        </Grid>
    </Grid>
</UserControl>

ModalPresenterControl.xaml.cs

public partial class ModalPresenterControl : UserControl
{
    public FrameworkElement ViewToShow
    {
        get { return (FrameworkElement)GetValue(ViewToShowProperty); }
        set { SetValue(ViewToShowProperty, value); }
    }

    public static readonly DependencyProperty ViewToShowProperty =
        DependencyProperty.Register(nameof(ViewToShow), typeof(FrameworkElement), typeof(ModalPresenterControl), new FrameworkPropertyMetadata(null));

    public FrameworkElement ModalToShow
    {
        get { return (FrameworkElement)GetValue(ModalToShowProperty); }
        set { SetValue(ModalToShowProperty, value); }
    }

    public static readonly DependencyProperty ModalToShowProperty =
        DependencyProperty.Register(nameof(ModalToShow), typeof(FrameworkElement), typeof(ModalPresenterControl), new FrameworkPropertyMetadata(null));


    public ModalPresenterControl()
    {
        InitializeComponent();
    }
}

Usage.xaml

<ctrls:ModalPresenterControl ModalToShow="{Binding ActiveModal}">
    <ctrls:ModalPresenterControl.ViewToShow>
        <Grid>
            <ContentPresenter Content="{Binding ActiveView, Mode=OneWay}"/>
        </Grid>
    </ctrls:ModalPresenterControl.ViewToShow>
</ctrls:ModalPresenterControl>

Usage.xaml.cs

private DispatcherFrame frame;

private ContentControl activeView = new ContentControl();
public ContentControl ActiveView
{
    get { return activeView; }
    set { SetProperty(ref activeView, value); }
}

private FrameworkElement activeModal;
public FrameworkElement ActiveModal
{
    get { return activeModal; }
    set { SetProperty(ref activeModal, value); }
}

private void ShowModal()
{
    frame = new DispatcherFrame();

    ActiveModal = ...;
    Dispatcher.PushFrame(frame);
}

private void HideModal()
{
    frame.Continue = false;
    frame = null;
    ActiveModal = null;
}