// ModelMain.cs (модель)
public sealed class ModelMain
{
    private readonly NavigationService _navigationService;

	public ModelMain(NavigationService navigationService)
	{
	    _navigationService = navigationService;
	    
        AddWellCommand = new RelayCommand<Page>(page =>
        {
            var model = new EditModel(_navigationService);
            var page = new EditView {DataContext = model};
            page.Returning += AddEvent; // Нужно чтобы это событие срабатывало, при нажатии на кнопку в EditView. К кнопка подключена к команде [ public RelayCommand<Page> SaveChanges { get; private set; } ]
            _navigationService.Navigate(page);
        },
        page => true);
	}

    public void AddEvent(object sender, ReturnEventArgs<bool> e)
    {
    // ... 
    }
	
	public RelayCommand<Page> AddWellCommand { get; private set; }
}

// EditView.cs (представление)
public partial class EditView : Page
{
    public EditView()
    {
        InitializeComponent();
    }
    public void PageReturn(bool result)
    {
        RaiseReturning(new ReturnEventArgs<bool>(result));
    }
    private void RaiseReturning(ReturnEventArgs<bool> e)
    {
        var handler = Returning;
        if (handler != null) handler(this, e);
    }
    public event ReturnEventHandler<bool> Returning;
}

// EditModel.cs (модель педставления)
public sealed class EditModel
{
    private readonly NavigationService _navigationService;
    public DerectWellEditModel(NavigationService navigationService)
    {
	
	}
	
	public RelayCommand<Page> SaveChanges { get; private set; }
}

// ModelMain.cs (модель)
public sealed class ModelMain
{
    private readonly NavigationService _navigationService;
    public RelayCommand<Page> AddWellCommand { get; private set; }
	
	public ModelMain(NavigationService navigationService)
	{
	    _navigationService = navigationService;
	    
        AddWellCommand = new RelayCommand<Page>(page =>
        {
            var model = new EditModel(_navigationService);
            var page = new PageFunctionTest {DataContext = model};
            page.Returning += AddEvent; 
            _navigationService.Navigate(page);
        },
        page => true);
	}
    public void AddEvent(object sender, ReturnEventArgs<bool> e)
    {
    // ... 
    }	
}

// PageFunctionTest.cs (представление)
public partial class PageFunctionTest : PageFunction<string> 
{
    public PageFunctionTest() 
    {
        InitializeComponent();
    }
    private void Button_Click(object sender, RoutedEventArgs e) // Событие по кнопке
    {
        OnReturn(new ReturnEventArgs<string>("ОТВЕТ"));
    }
    protected override void OnReturn(ReturnEventArgs<string> e)
    {
        RaiseReturning(e);
        base.OnReturn(e);
    }
    private void RaiseReturning(ReturnEventArgs<string> e)
    {
        var handler = Returning;
        if (handler != null) handler(this, e);
    }
    public event ReturnEventHandler<string> Returning;
}

// PageFunctionTest.xaml (представления)
<PageFunction
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sys="clr-namespace:System;assembly=mscorlib" 
    x:TypeArguments="sys:String"
    x:Class="LF.Views.PageFunctionTest"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    mc:Ignorable="d"
    Title="PageFunctionTest">
    <Grid>
        <Button Content="Button" HorizontalAlignment="Left" Margin="51,150,0,0" VerticalAlignment="Top" Width="196" Click="Button_Click"/>
    </Grid>
</PageFunction>

// PageFunctionAbst.cs абстракный класс
public abstract class PageFunctionAbst<T> : PageFunction<T>
{
    protected PageFunctionEx()
    {
        KeepAlive = true;
    }
    public void PageReturn(T result)
    {
        OnReturn(new ReturnEventArgs<T>(result));
    }
    protected override void OnReturn(ReturnEventArgs<T> e)
    {
        RaiseReturning(e);
        base.OnReturn(e);
    }
    private void RaiseReturning(ReturnEventArgs<T> e)
    {
        var handler = Returning;
        if (handler != null) handler(this, e);
    }
    public event ReturnEventHandler<T> Returning;
}

// PageFunctionTest.cs теперь к текущей странице его наследую
public partial class PageFunctionTest : PageFunctionAbst<string> 
{
    public PageFunctionTest() 
    {
        InitializeComponent();
    }
}

<local:MyClass xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:local="clr-namespace:MyNamespace"
............./>
...
</local:MyClass>

<local:PageFunctionTest
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sys="clr-namespace:System;assembly=mscorlib" 
    xmlns:local="LF.Views"
    x:TypeArguments="sys:String"
    x:Class="LF.Views.PageFunctionTest"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    mc:Ignorable="d"
    Title="PageFunctionTest">
    <Grid>
        <Button Content="Button" HorizontalAlignment="Left" Margin="51,150,0,0" VerticalAlignment="Top" Width="196" Click="Button_Click"/>
    </Grid>
</local:PageFunctionTest>