回答編集履歴

- なんか堂々巡りですね^^;

- どうもprismユーザーと話が合わないのは、私がわかってないだけなんでしょうか？（だったらいいのですが^^;

-

- 理屈上は`RelativeSource`で`Window`とでもすれば引っ張ってこれますが、そんなのイヤすぎますよね？

-

- そもそもガッツリprismしている場合、`UserControl`の表示は↓のようになりませんか？（Prism Full App(.NET Core)テンプレートより）

- ```xaml

- <ContentControl prism:RegionManager.RegionName="{x:Static core:RegionNames.ContentRegion}" />

- ```

- `DependencyProperty`を設定するタイミングもないです（まあやりようはあるんでしょうけど）

-

- 一度Prism Full App(.NET Core)テンプレートを作っていただいて、`ViewA`・`ViewAViewModel`・`MessageService`の関係を見ていただけたらいいと思います。

-

- ---

-

- 例がないと話の前提が合いませんので雑に作りました（`Func<T,R>`が気持ち悪いのは気にしないでください^^;

- [NuGet Gallery | Prism.DryIoc 8.1.97](https://www.nuget.org/packages/Prism.DryIoc/8.1.97)

- [NuGet Gallery | ReactiveProperty 7.12.0](https://www.nuget.org/packages/ReactiveProperty/7.12.0)

-

- `TextBox`と`TextBlock`の組が４つあります。どれも動作は同じです（入力値の小文字が大文字になって表示される）

-

- ４つのうち１つだけおかしい（異質な）ものがあります。

-

- MainWindow.xaml

- ```xaml

- <Window

- x:Class="Questions362091.Views.MainWindow"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

- xmlns:prism="http://prismlibrary.com/"

- xmlns:views="clr-namespace:Questions362091.Views"

- Width="525"

- SizeToContent="Height">

- <StackPanel>

-

- <GroupBox Header="ベタ置き">

- <StackPanel>

- <TextBox Text="{Binding Input.Value, UpdateSourceTrigger=PropertyChanged}" />

- <TextBlock HorizontalAlignment="Center" Text="↓" />

- <TextBlock Text="{Binding Output.Value}" />

- </StackPanel>

- </GroupBox>

-

- <GroupBox Header="UserControl1">

- <views:UserControl1 />

- </GroupBox>

-

- <GroupBox Header="PrismUserControl1">

- <ContentControl prism:RegionManager.RegionName="ContentRegion" />

- </GroupBox>

-

- <GroupBox Header="UserControl2">

- <views:UserControl2 Converter="{Binding Converter}" Input="{Binding Input.Value}" />

- </GroupBox>

- </StackPanel>

- </Window>

- ```

-

- UserControl1.xaml

- ```xaml

- <UserControl

- x:Class="Questions362091.Views.UserControl1"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

- <StackPanel>

- <TextBox Text="{Binding Input.Value, UpdateSourceTrigger=PropertyChanged}" />

- <TextBlock HorizontalAlignment="Center" Text="↓" />

- <TextBlock Text="{Binding Output.Value}" />

- </StackPanel>

- </UserControl>

- ```

-

- PrismUserControl1.xaml

- ```xaml

- <UserControl

- x:Class="Questions362091.Views.PrismUserControl1"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

- <StackPanel>

- <TextBox Text="{Binding Input.Value, UpdateSourceTrigger=PropertyChanged}" />

- <TextBlock HorizontalAlignment="Center" Text="↓" />

- <TextBlock Text="{Binding Output.Value}" />

- </StackPanel>

- </UserControl>

- ```

-

- UserControl2.xaml

- ```xaml

- <UserControl

- x:Class="Questions362091.Views.UserControl2"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

- xmlns:views="clr-namespace:Questions362091.Views">

- <StackPanel>

- <TextBox Text="{Binding Input, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource AncestorType={x:Type views:UserControl2}}}" />

- <TextBlock HorizontalAlignment="Center" Text="↓" />

- <TextBlock Text="{Binding Output, RelativeSource={RelativeSource AncestorType={x:Type views:UserControl2}}}" />

- </StackPanel>

- </UserControl>

- ```

-

- UserControl2.xaml.cs

- ```C#

- using System;

- using System.Windows;

- using System.Windows.Controls;

-

- namespace Questions362091.Views

- {

- public partial class UserControl2 : UserControl

- {

- public string Input { get => (string)GetValue(InputProperty); set => SetValue(InputProperty, value); }

- public static readonly DependencyProperty InputProperty = DependencyProperty.Register(nameof(Input), typeof(string), typeof(UserControl2), new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, InputChanged));

- private static void InputChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

- {

- if (d is UserControl2 userControl2)

- userControl2.Output = userControl2.Converter?.Invoke((string)e.NewValue);

- }

-

- public string Output { get => (string)GetValue(OutputProperty); protected set => SetValue(OutputPropertyKey, value); }

- private static readonly DependencyPropertyKey OutputPropertyKey = DependencyProperty.RegisterReadOnly(nameof(Output), typeof(string), typeof(UserControl2), new());

- public static readonly DependencyProperty OutputProperty = OutputPropertyKey.DependencyProperty;

-

- public Func<string, string> Converter { get => (Func<string, string>)GetValue(ConverterProperty); set => SetValue(ConverterProperty, value); }

- public static readonly DependencyProperty ConverterProperty = DependencyProperty.Register(nameof(Converter), typeof(Func<string, string>), typeof(UserControl2), new((Func<string, string>)(s => s)));

-

- public UserControl2() => InitializeComponent();

- }

- }

- ```

-

- MainWindowViewModel.cs

- ```C#

- using Prism.Mvvm;

- using Prism.Regions;

- using Questions362091.Models;

- using Reactive.Bindings;

- using Reactive.Bindings.Extensions;

- using System;

-

- namespace Questions362091.ViewModels

- {

- public class MainWindowViewModel : BindableBase

- {

- public ReactiveProperty<string> Input { get; }

- public ReadOnlyReactiveProperty<string> Output { get; }

- public Func<string, string> Converter => model.Converter;

-

- private readonly Model model;

-

- public MainWindowViewModel(Model model, IRegionManager regionManager)

- {

- this.model = model;

- Input = model.Input.ToReactivePropertyAsSynchronized(x => x.Value);

- Output = model.Output.ToReadOnlyReactiveProperty();

- }

- }

- }

- ```

-

- PrismUserControl1ViewModel.cs

- ```C#

- using Prism.Mvvm;

- using Questions362091.Models;

- using Reactive.Bindings;

- using Reactive.Bindings.Extensions;

-

- namespace Questions362091.ViewModels

- {

- public class PrismUserControl1ViewModel : BindableBase

- {

- public ReactiveProperty<string> Input { get; }

- public ReadOnlyReactiveProperty<string> Output { get; }

-

- public PrismUserControl1ViewModel(Model model)

- {

- Input = model.Input.ToReactivePropertyAsSynchronized(x => x.Value);

- Output = model.Output.ToReadOnlyReactiveProperty();

- }

- }

- }

- ```

-

- Model.cs

- ```C#

- using Reactive.Bindings;

- using System;

- using System.Reactive.Linq;

-

- namespace Questions362091.Models

- {

- public class Model

- {

- public ReactivePropertySlim<string> Input { get; } = new();

- public ReadOnlyReactivePropertySlim<string> Output { get; }

- public Func<string, string> Converter { get; } = s => s?.ToUpper();

-

- public Model() => Output = Input.Select(Converter).ToReadOnlyReactivePropertySlim();

- }

- }

- ```

-

- App.xaml.cs

- ```C#

- using Prism.Ioc;

- using Prism.Regions;

- using Questions362091.Models;

- using Questions362091.Views;

- using System.Windows;

-

- namespace Questions362091

- {

- public partial class App

- {

- protected override Window CreateShell() => Container.Resolve<MainWindow>();

- protected override void OnInitialized()

- {

- base.OnInitialized();

- var regionManager = Container.Resolve<IRegionManager>();