Dialogs

The cornerstone of dialogs the DialogHost control. It’s a content control, meaning the underlying content over which the popup dialog will be displayed can be targeted; to a specific area of your app, or the entire Window content.

<md:DialogHost>
    <md:DialogHost.DialogContent>
        <dialogContent />
    </md:DialogHost.DialogContent>
    <mainContent />
</md:DialogHost>

When the dialog is open, the underlying content will be dimmed and disabled.

DialogHost.DialogContent (associated with DialogHost.DialogContentTemplate) is your typical XAML content object property for setting the content of your dialog. You can infer from this that you can use MVVM to bind content, but there are multiple ways of populating the content, showing the dialog, closing the dialog, and processing responses, so here’s a list of all the strategies for using the dialog (after the gif):

Open Dialog Strategies

DialogHost.OpenDialogCommand

<Button Command="{x:Static md:DialogHost.OpenDialogCommand}" />

RoutedCommand typically used from a button where optional content can be provided via the CommandParameter.

DialogHost.IsOpen

<md:DialogHost IsOpen="True" />

Dependency property, to be triggered from XAML, set from code-behind or via a binding. Content must be set in DialogHost.DialogContent.

DialogHost.Show

DialogHost.Show(viewOrModel);

Async/await based static API which can be used purely in code (for example from in a view model). Content can be passed directly to the dialog.

Close Dialog Strategies

DialogHost.CloseDialogCommand

<Button Command="{x:Static md:DialogHost.CloseDialogCommand}" />

RoutedCommand, typically used on buttons inside the dialog, where the command parameter will be passed along to the dialog response.

DialogHost.IsOpen

<md:DialogHost IsOpen="False" />

Dependency property, to be triggered from XAML, set from code-behind or via a binding.

Handle Close Strategies

The DialogClosingEventHandler delegate is key. It provides the parameter provided to DialogHost.CloseDialogCommand, and allows the pending close to be cancelled.

The following mechanisms allow handling of this event, via code-behind, MVVM practices, or just from the code API:

DialogHost.DialogClosing

<md:DialogHost DialogClosing="DialogHost_OnDialogClosing" />

Bubbling RoutedEvent, which could be used in code-behind.

DialogHost.DialogClosingAttached

<Button Command="{x:Static wpf:DialogHost.OpenDialogCommand}" md:DialogHost.DialogClosingAttached="DialogHost_OnDialogClosing" />

Attached property, which accepts a DialogClosingEventHandler which makes it easy to subscribe to the closing event in a more localized area of XAML.

DialogClosing.DialogClosingCallback

<md:DialogHost DialogClosingCallback="{Binding DialogClosingHandler}" />

Standard dependency property which enables the a DialogClosingEventHandler implementation to be bound in, typically from a view model.

DialogHost.Show

var result = await DialogHost.Show(viewOrModel, ClosingEventHandler);

The async response from this method returns the parameter provided when DialogHost.CloseDialogCommand was executed. As part of the Show() signature a DialogClosingEventHandler delegate can be provided to intercept the on-closing event, just prior to the close.

More Examples

More complete usage examples can be found in MainDemo.Wpf which is part of the Toolkit solution, primarily in MainDemo.Wpf/Dialogs.xaml.