Add CommandFactory class

samples/XCT.Sample/Pages/AboutPage.xaml

@@ -14,7 +14,11 @@
     <pages:BasePage.BindingContext>
         <viewmodels:AboutViewModel />
     </pages:BasePage.BindingContext>
-
+
+    <ContentPage.Behaviors>
+        <xct:EventToCommandBehavior EventName="Appearing" Command="{Binding PageAppearingCommand}"/>
+    </ContentPage.Behaviors>
+
     <pages:BasePage.Content>
         <StackLayout Padding="{StaticResource ContentPadding}">
             <Label Text="Thank you Xamarin Community Toolkit contributors"

samples/XCT.Sample/Pages/AboutPage.xaml.cs

@@ -1,9 +1,4 @@
 using System;
-using System.Linq;
-using Octokit;
-using Xamarin.CommunityToolkit.Sample.ViewModels;
-using Xamarin.Essentials;
-using Xamarin.Forms;
 
 namespace Xamarin.CommunityToolkit.Sample.Pages
 {
@@ -12,12 +7,6 @@ public partial class AboutPage : BasePage
 		public AboutPage()
 			=> InitializeComponent();
 
-		protected override async void OnAppearing()
-		{
-			base.OnAppearing();
-			await ((AboutViewModel)BindingContext).OnAppearing();
-		}
-
 		async void OnCloseClicked(object sender, EventArgs e)
 			=> await Navigation.PopModalAsync();
 	}

samples/XCT.Sample/Pages/Base/BasePage.cs

@@ -8,12 +8,12 @@ namespace Xamarin.CommunityToolkit.Sample.Pages
 {
 	public class BasePage : ContentPage
 	{
-		ICommand navigateCommand;
+		public BasePage() =>
+			NavigateCommand = CommandFactory.Create<SectionModel>(sectionModel => Navigation.PushAsync(PreparePage(sectionModel)));
 
 		public Color DetailColor { get; set; }
 
-		public ICommand NavigateCommand => navigateCommand ??= new AsyncCommand<SectionModel>(sectionModel
-			=> Navigation.PushAsync(PreparePage(sectionModel)));
+		public ICommand NavigateCommand { get; }
 
 		Page PreparePage(SectionModel model)
 		{

samples/XCT.Sample/Pages/Converters/ByteArrayToImageSourcePage.xaml

@@ -16,6 +16,10 @@
          </ResourceDictionary>
     </ContentPage.Resources>
 
+    <ContentPage.Behaviors>
+        <xct:EventToCommandBehavior EventName="Appearing" Command="{Binding PageAppearingCommand}"/>
+    </ContentPage.Behaviors>
+
     <pages:BasePage.Content>
 
         <StackLayout Orientation="Vertical" VerticalOptions="Center">

samples/XCT.Sample/Pages/Converters/ByteArrayToImageSourcePage.xaml.cs

@@ -1,16 +1,8 @@
-using Xamarin.CommunityToolkit.Sample.ViewModels.Converters;
-
-namespace Xamarin.CommunityToolkit.Sample.Pages.Converters
+namespace Xamarin.CommunityToolkit.Sample.Pages.Converters
 {
 	public partial class ByteArrayToImageSourcePage : BasePage
 	{
 		public ByteArrayToImageSourcePage()
 			=> InitializeComponent();
-
-		protected override async void OnAppearing()
-		{
-			base.OnAppearing();
-			await ((ByteArrayToImageSourceViewModel)BindingContext).OnAppearing();
-		}
 	}
 }

samples/XCT.Sample/Pages/Effects/TouchEffectPage.xaml.cs

@@ -1,5 +1,5 @@
 using System.Windows.Input;
-using Xamarin.Forms;
+using Xamarin.CommunityToolkit.ObjectModel;
 using Xamarin.Forms.Xaml;
 
 namespace Xamarin.CommunityToolkit.Sample.Pages.Effects
@@ -9,18 +9,18 @@ public partial class TouchEffectPage
 	{
 		public TouchEffectPage()
 		{
-			Command = new Command(() =>
+			Command = CommandFactory.Create(() =>
 			{
 				TouchCount++;
 				OnPropertyChanged(nameof(TouchCount));
 			});
-			LongPressCommand = new Command(() =>
+			LongPressCommand = CommandFactory.Create(() =>
 			{
 				LongPressCount++;
 				OnPropertyChanged(nameof(LongPressCount));
 			});
-			InitializeComponent();
 
+			InitializeComponent();
 		}
 
 		public ICommand Command { get; }

samples/XCT.Sample/Pages/TestCases/TouchEffectButtonPage.xaml.cs

@@ -1,15 +1,16 @@
 using System.Windows.Input;
-using Xamarin.Forms;
+using Xamarin.CommunityToolkit.ObjectModel;
 
 namespace Xamarin.CommunityToolkit.Sample.Pages.TestCases
 {
 	public partial class TouchEffectButtonPage
 	{
-		ICommand command;
-
 		public TouchEffectButtonPage()
-			=> InitializeComponent();
+		{
+			Command = CommandFactory.Create(() => DisplayAlert("Command executed ", null, "OK"));
+			InitializeComponent();
+		}
 
-		public ICommand Command => command ??= new Command(() => this.DisplayAlert("Command executed ", null, "OK"));
+		public ICommand Command { get; }
 	}
 }

samples/XCT.Sample/ViewModels/AboutViewModel.cs

@@ -18,7 +18,18 @@ public class AboutViewModel : BaseViewModel
 
 		string emptyViewText = "Loading data...";
 
-		ICommand selectedContributorCommand;
+		public AboutViewModel()
+		{
+			PageAppearingCommand = CommandFactory.Create(OnAppearing);
+			SelectedContributorCommand = CommandFactory.Create(async () =>
+			{
+				if (SelectedContributor == null)
+					return;
+
+				await Launcher.OpenAsync(SelectedContributor.HtmlUrl);
+				SelectedContributor = null;
+			});
+		}
 
 		public RepositoryContributor[] Contributors
 		{
@@ -38,14 +49,9 @@ public string EmptyViewText
 			set => SetProperty(ref emptyViewText, value);
 		}
 
-		public ICommand SelectedContributorCommand => selectedContributorCommand ??= new AsyncCommand(async () =>
-		{
-			if (SelectedContributor is null)
-				return;
+		public ICommand PageAppearingCommand { get; }
 
-			await Launcher.OpenAsync(SelectedContributor.HtmlUrl);
-			SelectedContributor = null;
-		});
+		public ICommand SelectedContributorCommand { get; }
 
 		public async Task OnAppearing()
 		{

samples/XCT.Sample/ViewModels/Base/BaseGalleryViewModel.cs

@@ -4,21 +4,22 @@
 using System.Windows.Input;
 using Xamarin.CommunityToolkit.ObjectModel;
 using Xamarin.CommunityToolkit.Sample.Models;
-using Xamarin.Forms;
 
 namespace Xamarin.CommunityToolkit.Sample.ViewModels
 {
 	public abstract class BaseGalleryViewModel : BaseViewModel
 	{
-		ICommand filterCommand;
-
-		public BaseGalleryViewModel() => Filter();
+		public BaseGalleryViewModel()
+		{
+			Filter();
+			FilterCommand = CommandFactory.Create(Filter);
+		}
 
 		public abstract IEnumerable<SectionModel> Items { get; }
 
 		public IEnumerable<SectionModel> FilteredItems { get; private set; }
 
-		public ICommand FilterCommand => filterCommand ??= new Command(Filter);
+		public ICommand FilterCommand { get; }
 
 		public string FilterValue { private get; set; }
 

samples/XCT.Sample/ViewModels/Behaviors/EventToCommandBehaviorViewModel.cs

@@ -1,20 +1,21 @@
 using System.Windows.Input;
-using Xamarin.Forms;
+using Xamarin.CommunityToolkit.ObjectModel;
 
 namespace Xamarin.CommunityToolkit.Sample.ViewModels.Behaviors
 {
 	public class EventToCommandBehaviorViewModel : BaseViewModel
 	{
-		ICommand incrementCommand;
-
 		int clickCount;
 
-		public ICommand IncrementCommand => incrementCommand ??= new Command(() => ClickCount++);
+		public EventToCommandBehaviorViewModel() =>
+			IncrementCommand = CommandFactory.Create(() => ClickCount++);
 
 		public int ClickCount
 		{
 			get => clickCount;
 			set => SetProperty(ref clickCount, value);
 		}
+
+		public ICommand IncrementCommand { get; }
 	}
 }

samples/XCT.Sample/ViewModels/Behaviors/MaxLengthReachedBehaviorViewModel.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Windows.Input;
-using Xamarin.Forms;
+using Xamarin.CommunityToolkit.ObjectModel;
 
 namespace Xamarin.CommunityToolkit.Sample.ViewModels.Behaviors
 {
@@ -17,7 +17,7 @@ public string CommandExecutions
 		public ICommand MaxLengthReachedCommand { get; }
 
 		public MaxLengthReachedBehaviorViewModel()
-			=> MaxLengthReachedCommand = new Command<string>(OnCommandExecuted);
+			=> MaxLengthReachedCommand = CommandFactory.Create<string>(OnCommandExecuted);
 
 		void OnCommandExecuted(string text)
 			=> CommandExecutions += string.Format("MaxLength reached with value: '{0}'.", text) + Environment.NewLine;

samples/XCT.Sample/ViewModels/Behaviors/UserStoppedTypingBehaviorViewModel.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Windows.Input;
-using Xamarin.Forms;
+using Xamarin.CommunityToolkit.ObjectModel;
 
 namespace Xamarin.CommunityToolkit.Sample.ViewModels.Behaviors
 {
@@ -21,7 +21,7 @@ public string PerformedSearches
 		#endregion Properties
 
 		public UserStoppedTypingBehaviorViewModel()
-			=> SearchCommand = new Command<string>(PerformSearch);
+			=> SearchCommand = CommandFactory.Create<string>(PerformSearch);
 
 		void PerformSearch(string searchTerms)
 			=> PerformedSearches += string.Format("Performed search for '{0}'.", searchTerms) + Environment.NewLine;

samples/XCT.Sample/ViewModels/Converters/ByteArrayToImageSourceViewModel.cs

@@ -1,7 +1,9 @@
 using System.Linq;
 using System.Net.Http;
 using System.Threading.Tasks;
+using System.Windows.Input;
 using Octokit;
+using Xamarin.CommunityToolkit.ObjectModel;
 
 namespace Xamarin.CommunityToolkit.Sample.ViewModels.Converters
 {
@@ -25,6 +27,11 @@ public bool IsBusy
 			set => SetProperty(ref isBusy, value);
 		}
 
+		public ICommand PageAppearingCommand { get; }
+
+		public ByteArrayToImageSourceViewModel() =>
+			PageAppearingCommand = CommandFactory.Create(OnAppearing);
+
 		public async Task OnAppearing()
 		{
 			try

samples/XCT.Sample/ViewModels/Converters/ItemSelectedEventArgsViewModel.cs

@@ -15,7 +15,7 @@ public class ItemSelectedEventArgsViewModel
 				new Person() { Id = 3, Name = "Person 3" }
 			};
 
-		public ICommand ItemSelectedCommand { get; private set; } = new AsyncCommand<Person>(person
-			=> Application.Current.MainPage.DisplayAlert("Item Tapped: ", person.Name, "Cancelf"));
+		public ICommand ItemSelectedCommand { get; } =
+			CommandFactory.Create<Person>(person => Application.Current.MainPage.DisplayAlert("Item Tapped: ", person.Name, "Cancelf"));
 	}
 }

samples/XCT.Sample/ViewModels/Converters/ItemTappedEventArgsViewModel.cs

@@ -15,8 +15,8 @@ public class ItemTappedEventArgsViewModel
 				new Person() { Id = 3, Name = "Person 3" }
 			};
 
-		public ICommand ItemTappedCommand { get; private set; } = new AsyncCommand<Person>(person
-			=> Application.Current.MainPage.DisplayAlert("Item Tapped: ", person.Name, "Cancel"));
+		public ICommand ItemTappedCommand { get; } =
+			CommandFactory.Create<Person>(person => Application.Current.MainPage.DisplayAlert("Item Tapped: ", person.Name, "Cancel"));
 	}
 
 	public class Person

samples/XCT.Sample/ViewModels/Converters/ListIsNullOrEmptyViewModel.cs

@@ -1,4 +1,5 @@
-using Xamarin.CommunityToolkit.ObjectModel;
+using Xamarin.CommunityToolkit.Helpers;
+using Xamarin.CommunityToolkit.ObjectModel;
 using Xamarin.Forms;
 
 namespace Xamarin.CommunityToolkit.Sample.ViewModels.Converters
@@ -9,15 +10,15 @@ public class ListIsNullOrEmptyViewModel : BaseViewModel
 
 		public ListIsNullOrEmptyViewModel()
 		{
-			AddItemCommand = new Command(() =>
+			AddItemCommand = CommandFactory.Create(() =>
 			{
 				Items.Add(new Person
 				{
 					Id = Items.Count,
 					Name = $"Person {Items.Count}"
 				});
 			});
-			RemoveItemCommand = new Command(() => Items.RemoveAt(0));
+			RemoveItemCommand = CommandFactory.Create(() => Items.RemoveAt(0));
 
 			// ListIsNullOrEmptyConvertor needs to know that Items are updated
 			Items.CollectionChanged += (sender, e) => OnPropertyChanged(nameof(Items));

samples/XCT.Sample/ViewModels/Markup/SearchViewModel.cs

@@ -8,8 +8,6 @@ namespace Xamarin.CommunityToolkit.Sample.ViewModels.Markup
 {
 	public class SearchViewModel : BaseViewModel
 	{
-		ICommand backCommand, likeCommand, openTwitterSearchCommand, openHelpCommand;
-
 		public string SearchText { get; set; }
 
 		public List<Tweet> SearchResults { get; set; }
@@ -54,15 +52,20 @@ public SearchViewModel()
 					},
 				}
 			};
+
+			BackCommand = new RelayCommand(Back);
+			LikeCommand = new RelayCommand<Tweet>(Like);
+			OpenTwitterSearchCommand = new RelayCommandAsync(OpenTwitterSearch);
+			OpenHelpCommand = new RelayCommandAsync(OpenHelp);
 		}
 
-		public ICommand BackCommand => backCommand ??= new RelayCommand(Back);
+		public ICommand BackCommand { get; }
 
-		public ICommand LikeCommand => likeCommand ??= new RelayCommand<Tweet>(Like);
+		public ICommand LikeCommand { get; }
 
-		public ICommand OpenTwitterSearchCommand => openTwitterSearchCommand ??= new RelayCommandAsync(OpenTwitterSearch);
+		public ICommand OpenTwitterSearchCommand { get; }
 
-		public ICommand OpenHelpCommand => openHelpCommand ??= new RelayCommandAsync(OpenHelp);
+		public ICommand OpenHelpCommand { get; }
 
 		void Back() { }