Enable Nullable

.editorconfig

@@ -107,3 +107,9 @@ csharp_new_line_before_catch = true
 csharp_new_line_before_finally = true
 csharp_new_line_before_members_in_object_initializers = true
 csharp_new_line_before_members_in_anonymous_types = true
+
+# SA1011: Closing square brackets should be spaced correctly
+dotnet_diagnostic.SA1011.severity = none
+
+# CS4014: Because this call is not awaited, execution of the current method continues before the call is completed
+dotnet_diagnostic.CS4014.severity = error

Directory.Build.props

@@ -2,7 +2,9 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
   <PropertyGroup>
-    <LangVersion>8.0</LangVersion>
+    <LangVersion>9.0</LangVersion>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>nullable</WarningsAsErrors>
   </PropertyGroup>
 
 

Xamarin.CommunityToolkit.ruleset

@@ -15,7 +15,6 @@
     <Rule Id="SA1008" Action="Warning" />
     <Rule Id="SA1009" Action="Warning" />
     <Rule Id="SA1010" Action="Warning" />
-    <Rule Id="SA1011" Action="Warning" />
     <Rule Id="SA1012" Action="Warning" />
     <Rule Id="SA1013" Action="Warning" />
     <Rule Id="SA1014" Action="Warning" />

azure-pipelines.yml

@@ -7,10 +7,12 @@ variables:
   #MONO_VERSION: 6_4_0
   #XCODE_VERSION: 11.4
   NETCORE_VERSION: '5.0.x'
-  NETCORE_TEST_VERSION: '5.0.x'
+  NETCORE_TEST_VERSION_3_1: '3.1.x'
+  NETCORE_TEST_VERSION_2_1: '2.1.x'
   RunPoliCheck: 'false'
   PathToCsproj: 'src/CommunityToolkit/Xamarin.CommunityToolkit/Xamarin.CommunityToolkit.csproj'
   PathToMarkupCsproj: 'src/Markup/Xamarin.CommunityToolkit.Markup/Xamarin.CommunityToolkit.Markup.csproj'
+  PathToUnitTestCsproj: 'src/CommunityToolkit/Xamarin.CommunityToolkit.UnitTests/Xamarin.CommunityToolkit.UnitTests.csproj'
   PathToSln: 'samples/XCT.Sample.sln'
 
 resources:
@@ -68,6 +70,21 @@ jobs:
     pool:
       vmImage: windows-2019
     steps:
+      - task: UseDotNet@2
+        displayName: 'Install .NET SDK'
+        inputs:
+          version: $(NETCORE_VERSION)
+          includePreviewVersions: false
+      - task: UseDotNet@2
+        displayName: 'Install .NET 3.1 Test SDK'
+        inputs:
+          version: $(NETCORE_TEST_VERSION_3_1)
+          includePreviewVersions: false
+      - task: UseDotNet@2
+        displayName: 'Install .NET 2.1 Test SDK'
+        inputs:
+          version: $(NETCORE_TEST_VERSION_2_1)
+          includePreviewVersions: false
       # if this is a tagged build, then update the version number
       - powershell: |
           $buildSourceBranch = "$(Build.SourceBranch)"
@@ -112,12 +129,10 @@ jobs:
 #          command: 'custom'
 #          custom: 'nuget'
 #          arguments: 'push --source https://nuget.pkg.github.com/xamarin/index.json --api-key $(GitHub.NuGet.Token) "$(Build.ArtifactStagingDirectory)\nuget\*.nupkg"'
-      - task: DotNetCoreCLI@2
-        displayName: Run Tests
+      - task: CmdLine@2
+        displayName: 'Run Unit Tests'
         inputs:
-          command: test
-          projects: '**/*.UnitTests.csproj'
-          arguments: '--configuration Release --collect "Code coverage"'
+          script: dotnet test $(PathToUnitTestCsproj) -c Release --collect "Code coverage" -p:BuildInParallel=false
       # publish the packages
       - task: PublishBuildArtifacts@1
         displayName: 'Publish Unsigned NuGets'
@@ -161,27 +176,28 @@ jobs:
       #  displayName: Switch to the latest Xcode
       # restore, build and pack the packages
       - task: UseDotNet@2
-        displayName: 'Use .Net Core sdk'
+        displayName: 'Install .NET SDK'
         inputs:
           version: $(NETCORE_VERSION)
           includePreviewVersions: false
       - task: UseDotNet@2
-        displayName: 'Use .Net Core sdk'
+        displayName: 'Install .NET 3.1 Test SDK'
         inputs:
-          version: $(NETCORE_TEST_VERSION)
+          version: $(NETCORE_TEST_VERSION_3_1)
           includePreviewVersions: false
-      - task: MSBuild@1
-        displayName: Build Solution
+      - task: UseDotNet@2
+        displayName: 'Install .NET 2.1 Test SDK'
         inputs:
-          solution: $(PathToCsproj)
-          configuration: Release
-          msbuildArguments: '/restore /t:Build /p:ContinuousIntegrationBuild=true /p:Deterministic=false'
-      - task: MSBuild@1
-        displayName: Pack NuGets
+          version: $(NETCORE_TEST_VERSION_2_1)
+          includePreviewVersions: false
+      - task: CmdLine@2
+        displayName: 'Build Solution'
         inputs:
-          solution: $(PathToCsproj)
-          configuration: Release
-          msbuildArguments: '/t:Pack /p:PackageVersion=$(NugetPackageVersion) /p:PackageOutputPath="$(Build.ArtifactStagingDirectory)/nuget"'
+          script: 'mono /Applications/Visual\ studio.app/Contents/Resources/lib/monodevelop/bin/MSBuild/Current/bin/MSBuild.dll $(PathToCsproj) /p:Configuration=Release /restore /t:Build /p:ContinuousIntegrationBuild=true /p:Deterministic=false'
+      - task: CmdLine@2
+        displayName: 'Pack NuGets'
+        inputs:
+          script: 'mono /Applications/Visual\ studio.app/Contents/Resources/lib/monodevelop/bin/MSBuild/Current/bin/MSBuild.dll $(PathToCsproj) /p:Configuration=Release /t:Pack /p:PackageVersion=$(NugetPackageVersion) /p:PackageOutputPath="$(Build.ArtifactStagingDirectory)/nuget"'
 
   - ${{ if eq(variables['System.TeamProject'], 'devdiv') }}:
     - template: sign-artifacts/jobs/v2.yml@internal-templates

samples/XCT.Sample.Android/SplashActivity.cs

@@ -9,7 +9,7 @@ namespace Xamarin.CommunityToolkit.Sample.Droid
 	[Activity(Label = "XamarinCommunityToolkitSample", Icon = "@mipmap/icon", Theme = "@style/SplashTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
 	public class SplashActivity : AppCompatActivity
 	{
-		protected override void OnCreate(Bundle savedInstanceState)
+		protected override void OnCreate(Bundle? savedInstanceState)
 		{
 			base.OnCreate(savedInstanceState);
 			var intent = new Intent(this, typeof(MainActivity));

samples/XCT.Sample.UWP/App.xaml.cs

@@ -85,7 +85,7 @@ protected override void OnLaunched(LaunchActivatedEventArgs e)
 		/// </summary>
 		/// <param name="sender">The Frame which failed navigation</param>
 		/// <param name="e">Details about the navigation failure</param>
-		void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
+		void OnNavigationFailed(object? sender, NavigationFailedEventArgs e)
 		{
 			throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
 		}
@@ -97,7 +97,7 @@ void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
 		/// </summary>
 		/// <param name="sender">The source of the suspend request.</param>
 		/// <param name="e">Details about the suspend request.</param>
-		void OnSuspending(object sender, SuspendingEventArgs e)
+		void OnSuspending(object? sender, SuspendingEventArgs e)
 		{
 			var deferral = e.SuspendingOperation.GetDeferral();
 

samples/XCT.Sample.iOS/Renderers/NoLineNavigationRenderer.cs

@@ -25,8 +25,11 @@ public override void ViewWillAppear(bool animated)
 			// Newest iOS version fix - trycatch isn't optimal
 			try
 			{
-				NavigationBar.ScrollEdgeAppearance.ShadowImage = new UIKit.UIImage();
-				NavigationBar.ScrollEdgeAppearance.ShadowColor = null;
+				if (NavigationBar.ScrollEdgeAppearance != null)
+				{
+					NavigationBar.ScrollEdgeAppearance.ShadowImage = new UIKit.UIImage();
+					NavigationBar.ScrollEdgeAppearance.ShadowColor = null;
+				}
 			}
 			catch (Exception)
 			{

samples/XCT.Sample.sln

@@ -18,9 +18,9 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Xamarin.CommunityToolkit.Sa
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{F695F5E8-420F-475F-A4CF-F5BB3FA6E818}"
 	ProjectSection(SolutionItems) = preProject
-		.editorconfig = .editorconfig
-		Directory.Build.props = Directory.Build.props
-		Xamarin.CommunityToolkit.ruleset = Xamarin.CommunityToolkit.ruleset
+		..\.editorconfig = ..\.editorconfig
+		..\Directory.Build.props = ..\Directory.Build.props
+		..\Xamarin.CommunityToolkit.ruleset = ..\Xamarin.CommunityToolkit.ruleset
 	EndProjectSection
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Xamarin.CommunityToolkit.Sample.WPF", "XCT.Sample.WPF\Xamarin.CommunityToolkit.Sample.WPF.csproj", "{C4D6CD2D-8DF4-4D46-936C-1AB31C87B5EA}"
@@ -62,6 +62,7 @@ Global
 		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Debug|x86.Build.0 = Debug|Any CPU
 		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Release|Any CPU.Build.0 = Release|Any CPU
+		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Release|Any CPU.Deploy.0 = Release|Any CPU
 		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Release|ARM.ActiveCfg = Release|Any CPU
 		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Release|ARM.Build.0 = Release|Any CPU
 		{8B80BFA6-7B19-4DE7-BD97-7D84194AD0C2}.Release|iPhone.ActiveCfg = Release|Any CPU
@@ -191,6 +192,8 @@ Global
 		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Debug|x86.Build.0 = Debug|x86
 		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Debug|x86.Deploy.0 = Debug|x86
 		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Release|Any CPU.ActiveCfg = Release|x86
+		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Release|Any CPU.Build.0 = Release|x86
+		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Release|Any CPU.Deploy.0 = Release|x86
 		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Release|ARM.ActiveCfg = Release|ARM
 		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Release|ARM.Build.0 = Release|ARM
 		{91C748B4-E9ED-4543-880A-26747B03DE3A}.Release|ARM.Deploy.0 = Release|ARM

samples/XCT.Sample/App.xaml.cs

@@ -1,4 +1,5 @@
-using Xamarin.CommunityToolkit.Helpers;
+using System.Globalization;
+using Xamarin.CommunityToolkit.Helpers;
 using Xamarin.CommunityToolkit.Sample.Pages;
 using Xamarin.CommunityToolkit.Sample.Resx;
 using Xamarin.Forms.PlatformConfiguration;
@@ -14,6 +15,7 @@ public App()
 
 			LocalizationResourceManager.Current.PropertyChanged += (sender, e) => AppResources.Culture = LocalizationResourceManager.Current.CurrentCulture;
 			LocalizationResourceManager.Current.Init(AppResources.ResourceManager);
+			LocalizationResourceManager.Current.CurrentCulture = new CultureInfo("en");
 
 			InitializeComponent();
 			MainPage = new BaseNavigationPage(new WelcomePage());

samples/XCT.Sample/Helpers/RelayCommand.cs

@@ -7,25 +7,21 @@ namespace Xamarin.CommunityToolkit.Sample
 {
 	public class RelayCommand : ICommand
 	{
-		readonly Action execute;
-		readonly Func<Task> asyncExecute;
+		readonly Action? execute;
+		readonly Func<Task>? asyncExecute;
+		readonly Func<bool>? canExecute;
 
-		Func<bool> canExecute;
 		int executingCount;
 
-		public RelayCommand(Action execute, Func<bool> canExecute = null)
+		public RelayCommand(Action execute, Func<bool>? canExecute = null)
 		{
-			if (execute == null)
-				throw new ArgumentNullException(nameof(execute));
-			this.execute = execute;
+			this.execute = execute ?? throw new ArgumentNullException(nameof(execute));
 			this.canExecute = canExecute;
 		}
 
-		protected RelayCommand(Func<Task> execute, Func<bool> canExecute = null) // This ctor is protected here and public in a derived class, to allow simple initialization like new RelayCommand(MyMethod) without errors due to ambiguity
+		protected RelayCommand(Func<Task> execute, Func<bool>? canExecute = null) // This ctor is protected here and public in a derived class, to allow simple initialization like new RelayCommand(MyMethod) without errors due to ambiguity
 		{
-			if (execute == null)
-				throw new ArgumentNullException(nameof(execute));
-			asyncExecute = execute;
+			asyncExecute = execute ?? throw new ArgumentNullException(nameof(execute));
 			this.canExecute = canExecute;
 		}
 
@@ -34,7 +30,7 @@ public RelayCommand(Action execute, Func<bool> canExecute = null)
 		/// </summary>
 		/// <param name="parameter">Ignored; this is the paremeterless command class</param>
 		/// <returns></returns>
-		public bool CanExecute(object parameter = null)
+		public bool CanExecute(object? parameter = null)
 		{
 			try
 			{
@@ -47,15 +43,12 @@ public bool CanExecute(object parameter = null)
 			}
 		}
 
-		public event EventHandler CanExecuteChanged;
+		public event EventHandler? CanExecuteChanged;
 
-		public void RaiseCanExecuteChanged()
-		{
-			CanExecuteChanged?.Invoke(this, EventArgs.Empty);
-		}
+		public void RaiseCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);
 
 		// Asynchronous command handling based on http://stackoverflow.com/a/31595509/6043538
-		public async void Execute(object parameter = null)
+		public async void Execute(object? parameter = null)
 		{
 			var couldExecuteBeforeExecute = CanExecute();
 			if (!couldExecuteBeforeExecute)
@@ -70,8 +63,10 @@ public async void Execute(object parameter = null)
 			{
 				if (execute != null)
 					execute();
-				else
+				else if (asyncExecute != null)
 					await asyncExecute();
+				else
+					throw new Exception("Execute is null");
 			}
 			catch (Exception ex)
 			{
@@ -89,31 +84,30 @@ public async void Execute(object parameter = null)
 
 	public class RelayCommandAsync : RelayCommand
 	{
-		public RelayCommandAsync(Func<Task> execute, Func<bool> canExecute = null)
-			: base(execute, canExecute) { } // This ctor is public here and protected in the base class, to allow simple initialization like new RelayCommandAsync(MyMethod) without errors due to ambiguity
+		public RelayCommandAsync(Func<Task> execute, Func<bool>? canExecute = null)
+			: base(execute, canExecute)
+		{
+			// This ctor is public here and protected in the base class, to allow simple initialization like new RelayCommandAsync(MyMethod) without errors due to ambiguity
+		}
 	}
 
 	public class RelayCommand<TParameter> : ICommand
 	{
-		readonly Action<TParameter> execute;
-		readonly Func<TParameter, Task> asyncExecute;
+		readonly Action<TParameter>? execute;
+		readonly Func<TParameter, Task>? asyncExecute;
+		readonly Func<TParameter?, bool>? canExecute;
 
-		Func<TParameter, bool> canExecute;
 		int executingCount;
 
-		public RelayCommand(Action<TParameter> execute, Func<TParameter, bool> canExecute = null)
+		public RelayCommand(Action<TParameter> execute, Func<TParameter?, bool>? canExecute = null)
 		{
-			if (execute == null)
-				throw new ArgumentNullException(nameof(execute));
-			this.execute = execute;
+			this.execute = execute ?? throw new ArgumentNullException(nameof(execute));
 			this.canExecute = canExecute;
 		}
 
-		protected RelayCommand(Func<TParameter, Task> execute, Func<TParameter, bool> canExecute = null) // This ctor is protected here and public in a derived class, to allow simple initialization like new RelayCommand(MyMethod) without errors due to ambiguity
+		protected RelayCommand(Func<TParameter, Task> execute, Func<TParameter?, bool>? canExecute = null) // This ctor is protected here and public in a derived class, to allow simple initialization like new RelayCommand(MyMethod) without errors due to ambiguity
 		{
-			if (execute == null)
-				throw new ArgumentNullException(nameof(execute));
-			asyncExecute = execute;
+			asyncExecute = execute ?? throw new ArgumentNullException(nameof(execute));
 			this.canExecute = canExecute;
 		}
 
@@ -122,11 +116,11 @@ public RelayCommand(Action<TParameter> execute, Func<TParameter, bool> canExecut
 		/// </summary>
 		/// <param name="parameter"></param>
 		/// <returns></returns>
-		public bool CanExecute(object parameter = null)
+		public bool CanExecute(object? parameter = null)
 		{
 			try
 			{
-				return canExecute != null ? canExecute((TParameter)parameter) : executingCount == 0;
+				return canExecute != null ? canExecute((TParameter?)parameter) : executingCount == 0;
 			}
 			catch (Exception ex)
 			{
@@ -135,12 +129,9 @@ public bool CanExecute(object parameter = null)
 			}
 		}
 
-		public event EventHandler CanExecuteChanged;
+		public event EventHandler? CanExecuteChanged;
 
-		public void RaiseCanExecuteChanged()
-		{
-			CanExecuteChanged?.Invoke(this, EventArgs.Empty);
-		}
+		public void RaiseCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);
 
 		// Asynchronous command handling based on http://stackoverflow.com/a/31595509/6043538
 		public async void Execute(object parameterAsObject)
@@ -159,13 +150,11 @@ public async void Execute(object parameterAsObject)
 				var parameter = (TParameter)parameterAsObject;
 
 				if (execute != null)
-				{
 					execute(parameter);
-				}
-				else
-				{
+				else if (asyncExecute != null)
 					await asyncExecute(parameter);
-				}
+				else
+					throw new Exception("Execute is null");
 			}
 			catch (Exception ex)
 			{
@@ -183,7 +172,10 @@ public async void Execute(object parameterAsObject)
 
 	public class RelayCommandAsync<TParameter> : RelayCommand<TParameter>
 	{
-		public RelayCommandAsync(Func<TParameter, Task> execute, Func<TParameter, bool> canExecute = null)
-			: base(execute, canExecute) { } // This ctor is public here and protected in the base class, to allow simple initialization like new RelayCommandAsync(MyMethod) without errors due to ambiguity
+		public RelayCommandAsync(Func<TParameter, Task> execute, Func<TParameter?, bool>? canExecute = null)
+			: base(execute, canExecute)
+		{
+			// This ctor is public here and protected in the base class, to allow simple initialization like new RelayCommandAsync(MyMethod) without errors due to ambiguity
+		}
 	}
 }