与使用 Frame 相对，最简单，最轻便的方法是为每个页面创建一个视图模型.然后创建一个包含所有页面并管理其选择的主视图模型. ContentControl 将使用分配给 ContentControl.ContentTemplate 属性的 DataTemplate 显示视图模型，或者在多页方案中使用 DataTemplateSelector分配给 ContentControl.ContentTemplateSelector 或隐式模板，方法是仅定义 DataTemplate.DataType 而没有 Key 属性:

The easiest and most lightweight way opposed to using a Frame, is to create a view model for each page. Then create a main view model which holds all pages and manages their selection. A ContentControl will display the view models using a DataTemplate assigned to the ContentControl.ContentTemplate property or in a multi page scenario either a DataTemplateSelector assigned to ContentControl.ContentTemplateSelector or implicit templates by only defining the DataTemplate.DataType without the Key attribute:

MainWindow.xaml

<Window>
  <Window.DataContext>
    <MainViewModel x:Key="MainViewModel" />
  </Window.DataContext>
  <Window.Resources>
    <!-- 
        The templates for the view of each page model.
        Can be moved to dedicated files.
    -->  
    <DataTemplate DataType="{x:Type LoginViewModel}">
      <Border Background="Coral">

        <!-- UserControl -->
        <local:LoginView />
      </Border>
    </DataTemplate>

    <DataTemplate DataType="{x:Type PageOneViewModel}">
      <Border Background="Red">
        <local:PageOne />
      </Border>
    </DataTemplate>    

    <DataTemplate DataType="{x:Type PageTwoViewModel}">
      <Border Background="DeepSkyBlue">
        <TextBox Text="{Binding PageTitle}" />
      </Border>
    </DataTemplate>    
  </Window.Resources>


<StackPanel>
    <Button Content="Load Login Page"
            Command="{Binding SelectPageFromIndexCommand}"
            CommandParameter="0" />
    <Button Content="Load Page One"
            Command="{Binding SelectPageFromIndexCommand}"
            CommandParameter="1" />
    <Button Content="Load Next Page"
            Command="{Binding SelectNextPageCommand}" />

    <!-- The actual page control -->
    <ContentControl Content="{Binding SelectedPage}" />
  </StackPanel>
</Window>

视图模型

MainViewModel.cs

class MainViewModel : INotifyPropertyChanged
{
  public MainViewModel()
  {
    this.Pages = new ObservableCollection<IPageViewModel>() 
    {
      new LoginViewModel(), 
      new PageOneViewModel(), 
      new PageTwoViewModel()
    };

    // Show startup page
    this.SelectedPage = this.Pages.First();
  }

  // Define the Execute and CanExecute delegates for the command
  // and pass them to the constructor
  public ICommand SelectPageFromIndexCommand => new SelectPageCommand(
    param => this.SelectedPage = this.Pages.ElementAt(int.Parse(param as string)),
    param => int.TryParse(param as string, out int index));

  // Define the Execute and CanExecute delegates for the command
  // and pass them to the constructor
  public ICommand SelectNextPageCommand => new SelectPageCommand(
    param => this.SelectedPage = this.Pages.ElementAt(this.Pages.IndexOf(this.SelectedPage) + 1),
    param => this.Pages.IndexOf(this.SelectedPage) + 1 < this.Pages.Count);

  private IPageViewModel selectedPage;    
  public IPageViewModel SelectedPage
  {
    get => this.selectedPage;
    set
    {
      if (object.Equals(value, this.selectedPage))
      {
        return;
      }

      this.selectedPage = value;
      OnPropertyChanged();
    }
  }

  private ObservableCollection<IPageViewModel> pages;    
  public ObservableCollection<IPageViewModel> Pages
  {
    get => this.pages;
    set
    {
      if (object.Equals(value, this.pages))
      {
        return;
      }

      this.pages = value;
      OnPropertyChanged();
    }
  }

  public event PropertyChangedEventHandler PropertyChanged;    
  protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
  {
    this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
  }
}

SelectPageCommand.cs

class SelectPageCommand : ICommand
{
  public SelectPageCommand(Action<object> executeDelegate, Predicate<object> canExecuteDelegate)
  {
    this.ExecuteDelegate = executeDelegate;
    this.CanExecuteDelegate = canExecuteDelegate;
  }

  private Predicate<object> CanExecuteDelegate { get; }
  private Action<object> ExecuteDelegate { get; }

  #region Implementation of ICommand

  public bool CanExecute(object parameter) => this.CanExecuteDelegate?.Invoke(parameter) ?? false;

  public void Execute(object parameter) => this.ExecuteDelegate?.Invoke(parameter);

  public event EventHandler CanExecuteChanged
  {
    add => CommandManager.RequerySuggested += value;
    remove => CommandManager.RequerySuggested -= value;
  }

  #endregion
}

页面模型

IPageViewModel.cs

// Base type for all pages
interface IPageViewModel : INotifyPropertyChanged
{
  public string PageTitle { get; set; }
}

LoginViewModel.cs

// BaseViewModel implementation. 
// Consider to introduce dedicated abstract class Page which implements IPageViewModel 
class LoginViewModel : BaseViewModel
{
  // Implementation
}

PageOneViewModel.cs

// BaseViewModel implementation. 
// Consider to introduce dedicated abstract class Page which implements IPageViewModel 
class PageOneViewModel : IPageViewModel 
{    
  // Implementation
}

PageTwoViewModel.cs

// BaseViewModel implementation. 
// Consider to introduce dedicated abstract class Page which implements IPageViewModel 
class PageTwoViewModel : IPageViewModel 
{    
  // Implementation
}