I'll explain how to navigate between screens using **WPF Prism** in C#.

As shown below, this is a process where the screen switches when you press a button.
(It's not a dialog — the content inside the screen itself switches.)

![image](/plants/wpf-prism-navigation/1.gif)

## Target Files (Example)

The files you need to code are **A through C** below.

```text
Views/
 |-MainWindowView.xaml（画面遷移元）　･･･A
 |-SampleNavigationView.xaml(画面遷移先)

ViewModels/
 |-MainWindowViewModel.cs（画面遷移元）　･･･B
 |-SampleNavigationViewModel.cs(画面遷移先)　･･･C

App.xaml.cs　･･･D
```

## MainWindowView.xaml (source of navigation) ･･･A

### ①Add a Command to the button

For the button on the View that navigation starts from, add the delegate command name via Binding on Command.

```xml
<Button Content="Sampleナビゲーション画面"
        FontSize="14"
        Margin="10"
        Padding="5"
        Command="{Binding SampleNavigationViewButton}"/>
```

## MainWindowViewModel.cs (source of navigation) ･･･B

### ②Add an IRegionManager field to the ViewModel

Add a private `IRegionManager` field to the ViewModel that navigation starts from, and set it in the constructor.

### ③Add the method that runs when the button is pressed

Add the delegate command property that receives the button-press event, and implement the Execute method for when the button is pressed.

▼Sample code for ② and ③ above
```cs
private IRegionManager _regionManager;  //// 画面遷移（ナビゲーション）

//// コンストラクタ
public MainWindowViewModel(IRegionManager regionManager)
{
    //// 画面遷移用（ナビゲーション）
    _regionManager = regionManager;

    SampleNavigationViewButton = new DelegateCommand(SampleNavigationViewButtonExecute);
}

public DelegateCommand SampleNavigationViewButton { get; }

private void SampleNavigationViewButtonExecute()
{
   //// 画面遷移処理（ナビゲーション）
   _regionManager.RequestNavigate("ContentRegion", nameof(SampleNavigationView));
}
```

## SampleNavigationViewModel.cs (navigation destination) ･･･C

### ④Implement the INavigationAware interface
Implement the **INavigationAware interface** and the **IRegionMemberLifetime interface** on the ViewModel that is the navigation destination.

※Added 2023/3/5
To release the ViewModel instance's memory, I've added an implementation of the IRegionMemberLifetime interface.

### ⑤Change the interface methods
Implementing INavigationAware adds `IsNavigationTarget` — set its return value to `true`, and set `KeepAlive` to `false`. This lets memory be released when the view is destroyed.

▼Sample code for ④ and ⑤ above
```cs
public class SampleTableEditViewModel : BindableBase, INavigationAware, IRegionMemberLifetime
{
    /// <summary>
    /// ViewModel破棄に伴いメモリ開放する際はfalse
    /// </summary>
    public bool KeepAlive { get; set; } = false;

    //// 各種処理

    public bool IsNavigationTarget(NavigationContext navigationContext)
    {
        //// RegionMemberLifetime(KeepAlive = false)でViewModelを破棄するため、こちらはTrue
        return true;
    }

    public virtual void OnNavigatedFrom(NavigationContext navigationContext)
    {
    }

    public virtual void OnNavigatedTo(NavigationContext navigationContext)
    {
    }
}
```

## App.xaml.cs　･･･D

### ⑥Register the View inside RegisterTypes

```cs
protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
    //// ナビゲーション画面
    containerRegistry.RegisterForNavigation<SampleNavigationView>();
}
```

Any View registered with `containerRegistry.RegisterForNavigation` becomes eligible for navigation.