实现此目的的一种简单方法是使用 IoC。创建子视图模型时，将主视图模型的引用传递给子视图模型，并将其作为私有只读变量保存。您现在可以访问所有主要的 VM publics 。
另一种解决方案可能是使用中介者模式。
敲出一个简单的 App 来演示 IoC 解决方案。
应用程序.xaml.cs
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
var window = new MainWindow() {DataContext = new MainWindowViewModel() };
window.Show();
}
}
MainWindowViewModel.cs
public class MainWindowViewModel : ViewModelBase
{
private string _statusMessage;
public string StatusMessage
{
get { return _statusMessage; }
set { _statusMessage = value; this.OnPropertyChanged("StatusMessage"); }
}
public ICommand OpenChildCommand { get; private set; }
public MainWindowViewModel()
{
this.StatusMessage = "No status";
this.OpenChildCommand = new DelegateCommand((o) => this.OpenChild());
}
private void OpenChild()
{
var window = new ChildWindow {DataContext = new ChildWindowViewModel(this)};
window.Show();
}
}
ChildWindowViewModel.cs
public class ChildWindowViewModel : ViewModelBase
{
private readonly MainWindowViewModel _mainvm;
public ChildWindowViewModel(MainWindowViewModel mainvm)
{
_mainvm = mainvm;
this.UpdateStatusCommand = new DelegateCommand((o) => this.UpdateStatus());
}
public ICommand UpdateStatusCommand { get; private set; }
private void UpdateStatus()
{
this._mainvm.StatusMessage = "New Status";
}
}
ViewModelBase.cs
public abstract class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, e);
}
}
}
委托命令.cs
public class DelegateCommand : ICommand
{
/// <summary>
/// Action to be performed when this command is executed
/// </summary>
private Action<object> executionAction;
/// <summary>
/// Predicate to determine if the command is valid for execution
/// </summary>
private Predicate<object> canExecutePredicate;
/// <summary>
/// Initializes a new instance of the DelegateCommand class.
/// The command will always be valid for execution.
/// </summary>
/// <param name="execute">The delegate to call on execution</param>
public DelegateCommand(Action<object> execute)
: this(execute, null)
{
}
/// <summary>
/// Initializes a new instance of the DelegateCommand class.
/// </summary>
/// <param name="execute">The delegate to call on execution</param>
/// <param name="canExecute">The predicate to determine if command is valid for execution</param>
public DelegateCommand(Action<object> execute, Predicate<object> canExecute)
{
if (execute == null)
{
throw new ArgumentNullException("execute");
}
this.executionAction = execute;
this.canExecutePredicate = canExecute;
}
/// <summary>
/// Raised when CanExecute is changed
/// </summary>
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
/// <summary>
/// Executes the delegate backing this DelegateCommand
/// </summary>
/// <param name="parameter">parameter to pass to predicate</param>
/// <returns>True if command is valid for execution</returns>
public bool CanExecute(object parameter)
{
return this.canExecutePredicate == null ? true : this.canExecutePredicate(parameter);
}
/// <summary>
/// Executes the delegate backing this DelegateCommand
/// </summary>
/// <param name="parameter">parameter to pass to delegate</param>
/// <exception cref="InvalidOperationException">Thrown if CanExecute returns false</exception>
public void Execute(object parameter)
{
if (!this.CanExecute(parameter))
{
throw new InvalidOperationException("The command is not valid for execution, check the CanExecute method before attempting to execute.");
}
this.executionAction(parameter);
}
}
主窗口.xaml
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<TextBlock Text="{Binding StatusMessage, Mode=OneWay}" />
<Button HorizontalAlignment="Center" VerticalAlignment="Center" Content="Open Child Window"
Command="{Binding Path=OpenChildCommand}"/>
</StackPanel>
ChildWindow.xaml
<Window x:Class="WpfApplication2.ChildWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="ChildWindow" Height="300" Width="300">
<Grid>
<Button HorizontalAlignment="Center" VerticalAlignment="Center" Content="UpdateStatus"
Command="{Binding Path=UpdateStatusCommand}" />
</Grid>
单击更新状态之前的图像
点击updatestatus后的图片
