Fix PR #4319 review comments: Shell navigation, Cancel canExecute, AOT-safe FromEventPattern, MAUI TFMs

- Add AppShell.xaml + AppShell.xaml.cs for MAUI Shell navigation
- Update App.xaml.cs to use new AppShell() instead of NavigationPage
- Fix LoginPage.xaml.cs: replace async void Subscribe with SelectMany/FromAsync + instance DisplayAlert
- Fix all three LoginViewModel.cs: Cancel uses Login.IsExecuting as canExecute via Subject<Unit> pattern
- Fix WPF LoginView.xaml.cs: use strongly-typed Observable.FromEventPattern overload
- Fix MAUI csproj: add proper platform-specific MAUI TFMs + OutputType=Exe

Agent-Logs-Url: https://github.com/reactiveui/ReactiveUI/sessions/93dee6e0-8644-4b85-996e-8a19bd5ccf27

Co-authored-by: glennawatson <5834289+glennawatson@users.noreply.github.com>

Author: Copilot

src/examples/ReactiveUI.Samples.Maui/App.xaml.cs

@@ -17,5 +17,5 @@ public partial class App : Application
 
     /// <inheritdoc/>
     protected override Window CreateWindow(IActivationState? activationState) =>
-        new(new NavigationPage(new LoginPage()));
+        new(new AppShell());
 }

src/examples/ReactiveUI.Samples.Maui/AppShell.xaml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<Shell
+    x:Class="ReactiveUI.Samples.Maui.AppShell"
+    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="clr-namespace:ReactiveUI.Samples.Maui"
+    Shell.NavBarIsVisible="False">
+
+    <ShellContent
+        ContentTemplate="{DataTemplate local:LoginPage}"
+        Route="LoginPage" />
+
+</Shell>

src/examples/ReactiveUI.Samples.Maui/AppShell.xaml.cs

@@ -0,0 +1,17 @@
+// Copyright (c) 2025 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+namespace ReactiveUI.Samples.Maui;
+
+/// <summary>
+/// Application shell providing Shell navigation for the MAUI sample.
+/// </summary>
+public partial class AppShell : Shell
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AppShell"/> class.
+    /// </summary>
+    public AppShell() => InitializeComponent();
+}

src/examples/ReactiveUI.Samples.Maui/LoginPage.xaml.cs

@@ -34,11 +34,12 @@ public LoginPage()
                 .DisposeWith(d);
 
             ViewModel.Login
-                .Subscribe(async success =>
-                    await (Shell.Current?.DisplayAlert(
+                .SelectMany(success => Observable.FromAsync(() =>
+                    DisplayAlert(
                         success ? "Login Successful" : "Login Failed",
                         success ? "Welcome!" : "Invalid credentials.",
-                        "OK") ?? Task.CompletedTask))
+                        "OK")))
+                .Subscribe()
                 .DisposeWith(d);
         });
     }

src/examples/ReactiveUI.Samples.Maui/LoginViewModel.cs

@@ -4,6 +4,7 @@
 // See the LICENSE file in the project root for full license information.
 
 using System.Reactive.Concurrency;
+using System.Reactive.Subjects;
 
 namespace ReactiveUI.Samples.Maui;
 
@@ -26,15 +27,20 @@ public LoginViewModel(IScheduler scheduler)
             vm => vm.Password,
             (user, pass) => !string.IsNullOrWhiteSpace(user) && !string.IsNullOrWhiteSpace(pass));
 
-        Cancel = ReactiveCommand.Create(() => { }, outputScheduler: scheduler);
+        var cancelSubject = new Subject<Unit>();
 
         Login = ReactiveCommand.CreateFromObservable(
             () => Observable
                 .Return(Password is "secret")
                 .Delay(TimeSpan.FromSeconds(1), scheduler)
-                .TakeUntil(Cancel),
+                .TakeUntil(cancelSubject),
             canLogin,
             scheduler);
+
+        Cancel = ReactiveCommand.Create(
+            () => cancelSubject.OnNext(Unit.Default),
+            Login.IsExecuting,
+            scheduler);
     }
 
     /// <summary>

src/examples/ReactiveUI.Samples.Maui/ReactiveUI.Samples.Maui.csproj

@@ -1,7 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net10.0</TargetFramework>
+    <TargetFrameworks>net10.0-android</TargetFrameworks>
+    <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows')) or $([MSBuild]::IsOSPlatform('osx'))">$(TargetFrameworks);net10.0-ios;net10.0-maccatalyst</TargetFrameworks>
+    <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net10.0-windows10.0.19041.0</TargetFrameworks>
+    <OutputType>Exe</OutputType>
     <UseMaui>true</UseMaui>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
@@ -10,6 +13,18 @@
     <IsAotCompatible>false</IsAotCompatible>
     <EnableTrimAnalyzer>false</EnableTrimAnalyzer>
     <EnableSingleFileAnalyzer>false</EnableSingleFileAnalyzer>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">15.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">15.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">24.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="$(TargetFramework.Contains('-windows'))">10.0.19041.0</SupportedOSPlatformVersion>
+    <TargetPlatformMinVersion Condition="$(TargetFramework.Contains('-windows'))">10.0.19041.0</TargetPlatformMinVersion>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(TargetFramework.Contains('-windows'))">
+    <WindowsPackageType>None</WindowsPackageType>
+    <GenerateAppxPackageOnBuild>false</GenerateAppxPackageOnBuild>
+    <PublishAppxPackage>false</PublishAppxPackage>
+    <AppxPackageSigningEnabled>false</AppxPackageSigningEnabled>
   </PropertyGroup>
 
   <ItemGroup>

src/examples/ReactiveUI.Samples.Winforms/LoginViewModel.cs

@@ -4,6 +4,7 @@
 // See the LICENSE file in the project root for full license information.
 
 using System.Reactive.Concurrency;
+using System.Reactive.Subjects;
 
 namespace ReactiveUI.Samples.Winforms;
 
@@ -26,15 +27,20 @@ public LoginViewModel(IScheduler scheduler)
             vm => vm.Password,
             (user, pass) => !string.IsNullOrWhiteSpace(user) && !string.IsNullOrWhiteSpace(pass));
 
-        Cancel = ReactiveCommand.Create(() => { }, outputScheduler: scheduler);
+        var cancelSubject = new Subject<Unit>();
 
         Login = ReactiveCommand.CreateFromObservable(
             () => Observable
                 .Return(Password is "secret")
                 .Delay(TimeSpan.FromSeconds(1), scheduler)
-                .TakeUntil(Cancel),
+                .TakeUntil(cancelSubject),
             canLogin,
             scheduler);
+
+        Cancel = ReactiveCommand.Create(
+            () => cancelSubject.OnNext(Unit.Default),
+            Login.IsExecuting,
+            scheduler);
     }
 
     /// <summary>

src/examples/ReactiveUI.Samples.Wpf/LoginView.xaml.cs

@@ -34,7 +34,9 @@ public LoginView()
                 .DisposeWith(d);
 
             // WPF PasswordBox doesn't support data binding, so marshal changes manually.
-            Observable.FromEventPattern(Password, nameof(PasswordBox.PasswordChanged))
+            Observable.FromEventPattern<RoutedEventHandler, RoutedEventArgs>(
+                    h => Password.PasswordChanged += h,
+                    h => Password.PasswordChanged -= h)
                 .Select(_ => Password.Password)
                 .BindTo(this, v => v.ViewModel!.Password)
                 .DisposeWith(d);

src/examples/ReactiveUI.Samples.Wpf/LoginViewModel.cs

@@ -4,6 +4,7 @@
 // See the LICENSE file in the project root for full license information.
 
 using System.Reactive.Concurrency;
+using System.Reactive.Subjects;
 
 namespace ReactiveUI.Samples.Wpf;
 
@@ -26,15 +27,20 @@ public LoginViewModel(IScheduler scheduler)
             vm => vm.Password,
             (user, pass) => !string.IsNullOrWhiteSpace(user) && !string.IsNullOrWhiteSpace(pass));
 
-        Cancel = ReactiveCommand.Create(() => { }, outputScheduler: scheduler);
+        var cancelSubject = new Subject<Unit>();
 
         Login = ReactiveCommand.CreateFromObservable(
             () => Observable
                 .Return(Password is "secret")
                 .Delay(TimeSpan.FromSeconds(1), scheduler)
-                .TakeUntil(Cancel),
+                .TakeUntil(cancelSubject),
             canLogin,
             scheduler);
+
+        Cancel = ReactiveCommand.Create(
+            () => cancelSubject.OnNext(Unit.Default),
+            Login.IsExecuting,
+            scheduler);
     }
 
     /// <summary>