在MVVM中切換視圖wpf

Question

我知道我的問題是常見的問題，但我發現的每個解決方案都不是我真正需要的解決方案。這是我的問題：我想能夠在mainWindow中的不同usercontrol之間切換。我發現的所有解決方案都包含在主窗口中有一個菜單，每個按鈕都帶有相應的userControl，如下例所示：https://rachel53461.wordpress.com/2011/12/18/navigation-with-mvvm-2/

但是我想要的更像是：在開始時，主窗口中有UserControl1 。在的UserControl1會有1個按鈕誰改變主窗口的一個新的用戶控件的內容（userControl2例如）

的主窗口

<Window x:Class="DataTemplateSO_Learning.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     xmlns:local="clr-namespace:DataTemplateSO_Learning" 
     Title="MainWindow" Height="350" Width="525"> 
    <Window.Resources>  
     <DataTemplate DataType="{x:Type local:EmployeeViewModel}"> 
      <local:EmployeeView/> 
     </DataTemplate> 
     <DataTemplate DataType="{x:Type local:DepartmentViewModel}"> 
      <local:DepartmentView/> 
     </DataTemplate> 
     <DataTemplate DataType="{x:Type local:MenuViewModel}"> 
      <local:MenuView/> 
     </DataTemplate> 
    </Window.Resources> 
    <DockPanel LastChildFill="True"> 
     <ContentControl x:Name="Pages" DockPanel.Dock="Right" Content="{Binding SelectedViewModel}"/> 
    </DockPanel> 
</Window> 

我的主窗口的CS的XAML：

public partial class MainWindow : Window 
{ 
    public MainWindow() 
    { 
     InitializeComponent(); 
     Pages.Content = new MenuView(); 
     this.DataContext = new NavigationViewModel(); 
    } 
} 

我的第一頁的XAML：

<UserControl x:Class="DataTemplateSO_Learning.MenuView" 
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:DataTemplateSO_Learning" 
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"> 
    <DockPanel LastChildFill="True"> 
     <StackPanel x:Name="navigation" DockPanel.Dock="Left" VerticalAlignment="Center"> 
      <Button Content="Employee" Command="{Binding EmpCommand}"></Button> 
      <Button Content="Department" Command="{Binding DeptCommand}"></Button> 
     </StackPanel> 
    </DockPanel> 
</UserControl> 

我的第一頁查看：

public partial class MenuView : UserControl 
{ 
    public MenuView() 
    { 
     InitializeComponent(); 
     this.DataContext = new MenuViewModel(); 
    } 
} 

我的第一頁的視圖模型：

class MenuViewModel 
{ 
    public ICommand EmpCommand { get; set; } 
    public ICommand DeptCommand { get; set; } 

    public MenuViewModel() 
    { 
     EmpCommand = new BaseCommand(OpenEmp); 
     DeptCommand = new BaseCommand(OpenDept); 
    } 

    private void OpenEmp(object obj) 
    { 
     SelectedViewModel = new EmployeeViewModel(); 
    } 
    private void OpenDept(object obj) 
    { 
     SelectedViewModel = new DepartmentViewModel(); 
    } 
} 

，當然他不知道「SelectedViewModel」，因爲它綁定到的主窗口

控制

my navigationViewModel：

class NavigationViewModel : INotifyPropertyChanged 
{ 
    private object selectedViewModel; 

    public object SelectedViewModel 
    { 
     get 
     { 
      return selectedViewModel; 
     } 
     set 
     { 
      selectedViewModel = value; 
      OnPropertyChanged("SelectedViewModel"); 
     } 
    } 

    public event PropertyChangedEventHandler PropertyChanged; 
    private void OnPropertyChanged(string propName) 
    { 
     if (PropertyChanged != null) 
     { 
      PropertyChanged(this, new PropertyChangedEventArgs(propName)); 
     } 
    } 

} 

非常感謝您的幫助！

Answer 1

例如，您可以注入MenuView或MenuViewModel與參考MainViewModel：

MainWindow.xaml.cs：

public partial class MainWindow : Window 
{ 
    public MainWindow() 
    { 
     InitializeComponent(); 
     var viewModel = new NavigationViewModel(); 
     viewModel.SelectedViewModel = new MenuViewModel(viewModel); 
     this.DataContext = viewModel; 
    } 
} 

MenuViewModel.cs：

class MenuViewModel 
{ 
    public ICommand EmpCommand { get; set; } 
    public ICommand DeptCommand { get; set; } 

    private readonly NavigationViewModel _navigationViewModel; 

    public MenuViewModel(NavigationViewModel navigationViewModel) 
    { 
     _navigationViewModel = navigationViewModel; 
     EmpCommand = new BaseCommand(OpenEmp); 
     DeptCommand = new BaseCommand(OpenDept); 
    } 

    private void OpenEmp(object obj) 
    { 
     _navigationViewModel.SelectedViewModel = new EmployeeViewModel(); 
    } 
    private void OpenDept(object obj) 
    { 
     _navigationViewModel.SelectedViewModel = new DepartmentViewModel(); 
    } 
} 

MenuView.xaml.cs：

public partial class MenuView : UserControl 
{ 
    public MenuView() 
    { 
     InitializeComponent(); 
    } 
}