Viewを内部に持つViewを複数生成できない

Viewを内部に持つViewを複数生成したいです。

ListBoxの数値を選択すると、選択された数値を受け取ったViewを表示するプログラムを作っています。
以前表示したViewは残して、異なる数値が選択された場合、新しくViewを生成するようにしたいです。

Viewの内部にViewを持っていると1→2に変えたときに下記のエラーが出ます。

ArgumentException: Region with the given name is already registered: ViewBRegion

WPF
.NET Core 3
Prism.Unity(7.2.0.1367)
ReactiveProperty(6.1.4)

<フォルダ構成>

ViewModelsフォルダ

MainWindowViewModel.cs
ViewAViewModel.cs
ViewBViewModel.cs

Viewsフォルダ

UserControls/ViewA.xaml
UserControls/ViewB.xaml
MainWindow.xaml

App.xaml

MainWindowViewModel.cs

C#
1using Prism.Mvvm;
2using Prism.Regions;
3using Reactive.Bindings;
4using System;
5using System.Collections.Generic;
6using Test.Views.UserControls;
7using Unity;
8
9namespace Test.ViewModels
10{
11    public class MainWindowViewModel : BindableBase
12    {
13        [Dependency]
14        public IRegionManager RegionManager { get; set; }
15        public List<int> NumberList { get; private set; }
16        public ReactiveProperty<int> SelectedNumber { get; set; }
17        public MainWindowViewModel()
18        {
19            this.NumberList = new List<int> { 1, 2, 3 };
20            this.SelectedNumber = new ReactiveProperty<int>();
21
22            this.SelectedNumber.Subscribe(_=>this.ChangeView()) ;
23        }
24
25        private void ChangeView()
26        {
27            if(RegionManager != null)
28            {
29                this.RegionManager.RequestNavigate("ContentRegion", nameof(ViewA), new NavigationParameters($"id={this.SelectedNumber.Value}"));
30            }
31        }
32    }
33}

ViewAViewModel.cs

C#
1using Prism.Commands;
2using Prism.Mvvm;
3using Prism.Regions;
4using Reactive.Bindings;
5using System;
6using System.Collections.Generic;
7using System.Linq;
8
9namespace Test.ViewModels
10{
11    public class ViewAViewModel : BindableBase, INavigationAware
12    {
13        public ReactiveProperty<string> Id { get; private set; }
14        public ViewAViewModel()
15        {
16            Id = new ReactiveProperty<string>();
17        }
18
19        public bool IsNavigationTarget(NavigationContext navigationContext)
20        {
21            return this.Id.Value == navigationContext.Parameters["id"] as string;
22        }
23
24        public void OnNavigatedFrom(NavigationContext navigationContext)
25        {
26
27        }
28
29        public void OnNavigatedTo(NavigationContext navigationContext)
30        {
31            this.Id.Value = navigationContext.Parameters["id"] as string;
32        }
33    }
34}

ViewBViewModel.cs

C#
1using Prism.Commands;
2using Prism.Mvvm;
3using System;
4using System.Collections.Generic;
5using System.Linq;
6
7namespace Test.ViewModels
8{
9    public class ViewBViewModel : BindableBase
10    {
11        public ViewBViewModel()
12        {
13
14        }
15    }
16}

MainWindow.xaml

xaml
1<Window x:Class="Test.Views.MainWindow"
2        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
3        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
4        xmlns:prism="http://prismlibrary.com/"
5        prism:ViewModelLocator.AutoWireViewModel="True"
6        Title="{Binding Title}" Height="350" Width="525" >
7    <StackPanel>
8        <ListBox ItemsSource="{Binding NumberList}" SelectedItem="{Binding SelectedNumber.Value}">
9            <ListBox.ItemTemplate>
10                <DataTemplate>
11                    <TextBlock Text="{Binding}"/>
12                </DataTemplate>
13            </ListBox.ItemTemplate>
14            <ListBox.ItemsPanel>
15                <ItemsPanelTemplate>
16                    <StackPanel Orientation="Horizontal"/>
17                </ItemsPanelTemplate>
18            </ListBox.ItemsPanel>
19        </ListBox>
20        <ContentControl prism:RegionManager.RegionName="ContentRegion" />
21    </StackPanel>
22</Window>

ViewA.xaml

xaml
1<UserControl x:Class="Test.Views.UserControls.ViewA"
2             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
3             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
4             xmlns:prism="http://prismlibrary.com/"             
5             prism:ViewModelLocator.AutoWireViewModel="True"
6             Loaded="UserControl_Loaded">
7    <StackPanel>
8        <TextBlock Text="{Binding Id.Value}"/>
9        <ContentControl prism:RegionManager.RegionName="ViewBRegion" />
10    </StackPanel>
11</UserControl>

ViewA.xaml.cs

C#
1using Prism.Ioc;
2using Prism.Regions;
3using System.Windows.Controls;
4using Unity;
5
6namespace Test.Views.UserControls
7{
8    /// <summary>
9    /// Interaction logic for ViewA
10    /// </summary>
11    public partial class ViewA : UserControl
12    {
13        [Dependency]
14        public IContainerExtension ContainerExtension { get; set; }
15        [Dependency]
16        public IRegionManager RegionManager { get; set; }
17        public ViewA()
18        {
19            InitializeComponent();
20        }
21
22        private void UserControl_Loaded(object sender, System.Windows.RoutedEventArgs e)
23        {
24            RegionManager.AddToRegion("ViewBRegion", ContainerExtension.Resolve<ViewB>());
25
26        }
27    }
28}

ViewB.xaml

xaml
1<UserControl x:Class="Test.Views.UserControls.ViewB"
2             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
3             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
4             xmlns:prism="http://prismlibrary.com/"             
5             prism:ViewModelLocator.AutoWireViewModel="True">
6    <Grid>
7        <TextBlock Text="ViewB"/>
8    </Grid>
9</UserControl>

app.xaml.cs

C#
1using Prism.Ioc;
2using Test.Views;
3using System.Windows;
4using Test.Views.UserControls;
5using Prism.Mvvm;
6using Test.ViewModels;
7
8namespace Test
9{
10    /// <summary>
11    /// Interaction logic for App.xaml
12    /// </summary>
13    public partial class App
14    {
15        protected override Window CreateShell()
16        {
17            return Container.Resolve<MainWindow>();
18        }
19
20        protected override void RegisterTypes(IContainerRegistry containerRegistry)
21        {
22            containerRegistry.RegisterForNavigation<ViewA>();
23        }
24        protected override void ConfigureViewModelLocator()
25        {
26            base.ConfigureViewModelLocator();
27            ViewModelLocationProvider.Register<ViewA, ViewAViewModel>();
28            ViewModelLocationProvider.Register<ViewB, ViewBViewModel>();
29
30        }
31    }
32}
33

行動規範の内容に同意します

回答1件

ベストアンサー

メッセージの通りRegionManagerに"ViewBRegion"を複数回登録しているから出ている例外です。
複数カ所で登録しているかまたは、Loadedイベントが複数回発生してないか確認してください。
また、おそらくその用途なら、ContainerRegistryに登録するのが適切であろうかと思われます。

投稿2019/12/11 06:54