diff --git a/src/Avalonia.Samples/MVVM/AdvancedMvvmDialogSample/README.adoc b/src/Avalonia.Samples/MVVM/AdvancedMvvmDialogSample/README.adoc new file mode 100644 index 0000000..5811a7d --- /dev/null +++ b/src/Avalonia.Samples/MVVM/AdvancedMvvmDialogSample/README.adoc @@ -0,0 +1,228 @@ += Enter the Title here +// --- D O N ' T T O U C H T H I S S E C T I O N --- +:toc: +:toc-placement!: +:tip-caption: :bulb: +:note-caption: :information_source: +:important-caption: :heavy_exclamation_mark: +:caution-caption: :fire: +:warning-caption: :warning: +// ---------------------------------------------------------- + + + +// Write a short summary here what this examples does +This example will show you how to write a service that will help you to show dialogs in your MVVM application + + + +// --- D O N ' T T O U C H T H I S S E C T I O N --- +toc::[] +// --------------------------------------------------------- + + +=== Difficulty +// Choose one of the below difficulties. You can just delete the ones you don't need. + +🐉 Hard 🐉 + + + +=== Buzz-Words + +// Write some buzz-words here. You can separate them by ", " +MVVM, Dialog, FileDialogs, TopLevel, Clipboard + + + +== Before we start + +We assume you already now how the MVVM pattern works and how dialogs, such as file dialogs, can be shown in general. You should also know what a https://docs.avaloniaui.net/docs/next/concepts/toplevel[[TopLevel\]]-control in Avalonia is and what it can be used for. + + +== The Solution : Use a DialogService to show a Dialog + +// This is where you explain the possible solution you provide in this sample. +// If you have more than one option to solve the issue, use Approach 1, Approach 2, ... + +=== Step 1: Add a DialogService-class + +In our project we add a folder called `Services`. Inside we will create a class called `DialogService` which inherits `AvaloniaObject`. + +NOTE: We need to inherit `AvaloniaObject` because we want to add register an `AttachedProperty` + +Let's add a `Dictionary` where we can store the registered mappings between the context (our `ViewModel`) and the `View`, which we want to interact with. + +```cs +public class DialogService : AvaloniaObject +{ + private static readonly Dictionary RegistrationMapper = + new Dictionary(); +} +``` + +In the next step we add an https://docs.avaloniaui.net/docs/next/concepts/attached-property[[AttachedProperty]] to our dialog service, which we call `Register`. Later we can bind any object to this property from every available `Visual`. + +```cs +/// +/// This property handles the registration of Views and ViewModel +/// +public static readonly AttachedProperty RegisterProperty = AvaloniaProperty.RegisterAttached( + "Register"); + +/// +/// Accessor for Attached property . +/// +public static void SetRegister(AvaloniaObject element, object value) +{ + element.SetValue(RegisterProperty, value); +} + +/// +/// Accessor for Attached property . +/// +public static object? GetRegister(AvaloniaObject element) +{ + return element.GetValue(RegisterProperty); +} +``` + +Now that we want to store or remove any new binding into our `Dictionary`, we need to listen to changes of the `RegsiterProperty`. We can add such a listener inside the static constructor. + +```c# +static DialogService() +{ + RegisterProperty.Changed.Subscribe(RegisterChanged); +} + +private static void RegisterChanged(AvaloniaPropertyChangedEventArgs e) +{ + if (e.Sender is not Visual sender) + { + throw new InvalidOperationException("The DialogService can only be registered on a Control"); + } + + // Unregister any old registered context + if (e.OldValue.Value != null) + { + RegistrationMapper.Remove(e.OldValue.Value); + } + + // Register any new context + if (e.NewValue.Value != null) + { + RegistrationMapper.Add(e.NewValue.Value, sender); + } +} +``` + + +=== Step 2: Add methods to lookup the view + +To make our life easier, we add can add some static functions to lookup the registered view. + +```C# +/// +/// Gets the associated for a given context. Returns null, if none was registered +/// +/// The context to lookup +/// The registered Visual for the context or null if none was found +public static Visual? GetVisualForContext(object context) +{ + return RegistrationMapper.TryGetValue(context, out var result) ? result : null; +} + +/// +/// Gets the parent for the given context. Returns null, if no TopLevel was found +/// +/// The context to lookup +/// The registered TopLevel for the context or null if none was found +public static TopLevel? GetTopLevelForContext(object context) +{ + return TopLevel.GetTopLevel(GetVisualForContext(context)); +} +``` + +If we are even more lazy, we can add some extension methods which we can use later to call a dialog in one line: + +```c# +/// +/// A helper class to manage dialogs via extension methods. Add more on your own +/// +public static class DialogHelper +{ + /// + /// Shows an open file dialog for a registered context, most likely a ViewModel + /// + /// The context + /// The dialog title or a default is null + /// Is selecting many files allowed? + /// An array of file names + /// if context was null + public static async Task?> OpenFileDialogAsync(this object? context, string? title = null, bool selectMany = true) + { + if (context == null) + { + throw new ArgumentNullException(nameof(context)); + } + + // lookup the TopLevel for the context + var topLevel = DialogService.GetTopLevelForContext(context); + + if(topLevel != null) + { + // Open the file dialog + var storageFiles = await topLevel.StorageProvider.OpenFilePickerAsync( + new FilePickerOpenOptions() + { + AllowMultiple = selectMany, + Title = title ?? "Select any file(s)" + }); + + // return the result + return storageFiles.Select(s => s.Name); + } + return null; + } + +} +``` + +=== Step 4: Usage + +Now that we have our `DialogService` created, we can start to register the `View` for our `ViewModel`. Thanks to our attached property, we can simply do: + +```xml + + + + +``` + +And in the `ViewModel` we can use our extension methods anywhere. The below sample command will ask the user to select a bunch of files: + +```c# +private async Task SelectFilesAsync() +{ + SelectedFiles = await this.OpenFileDialogAsync("Hello Avalonia"); +} +``` + +== Related + +There are more ways to show dialogs from the ViewModel, for example: + +* TODO[Interactions] +* https://github.com/AvaloniaCommunity/awesome-avalonia#mvvm--mvp--mvu[third party libs] +// Any related information or further readings goes here. + + + +// --------------- Ascii-Doc Cheat-Sheet ------------------ + +// visit: https://asciidoc.org +// visit: https://powerman.name/doc/asciidoc-compact + +// VS-Code has a great Add-In for Ascii docs: https://github.com/asciidoctor/asciidoctor-vscode/ \ No newline at end of file