如何回调自定义控件 WPF 中的代码

Question

I am using wpf. I created a custom control. In this control, I have multiple buttons. I can bind the button commands to the viewmodel. In this application, however, I need to callback to the code back file and not the viewmdoel. How can I do that?

Here is the example of my custom control:

<Grid>
    <StackPanel Orientation="Horizontal" Grid.Row="3">
        <Button Content="Button A" Command="{Binding SwitchToABCCommand}">
            <Button.Style>
                <Style TargetType="Button">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding CurRegion}" Value="ABC">
                            <Setter Property="Foreground" Value="Red" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </Button.Style>
        </Button>
        <Button Content="Button B" Command="{Binding SwitchToEFGCommand}">
            <Button.Style>
                <Style TargetType="Button">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding CurRegion}" Value="DEF">
                            <Setter Property="Foreground" Value="Red" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </Button.Style>
        </Button>
    </StackPanel>
</Grid>

Then I have another window using this custom control.

MainWindowViewModel.cs

public ICommand SwitchToABCCommand { get; }
public ICommand SwitchToDEFCommand { get; }
public MainWindowViewModel()
{
    SwitchToABCCommand = new DelegateCommand(HandleSwitchToABCCommand);
    SwitchToEFGCommand = new DelegateCommand(HandleSwitchToEFGCommand);
}
private void HandleSwitchToABCCommand()
{

}
private void HandleSwitchToDEFCommand()
{

}

And I want to callback to MainWindow.xaml.cs

private void SwitchToABC(object sender, RoutedEventArgs e)
{
}
private void SwitchToDEF(object sender, RoutedEventArgs e)
{
}

I have tried to do:

<Button Content="Button A" Click="SwitchToABC">

But this only can callback to MyCustomControl.xaml.cs . How can I call back to MainWindow.xaml.cs?

Thank you

Answer 1

The event handler must be defined in the same class as the XAML markup. If you define SwitchToABC in MyCustomControl.xaml.cs , you can call an event handler from the MainWindow from there though:

private void SwitchToABC(object sender, RoutedEventArgs e)
{
    MainWindow parentWindow = Window.GetWindow(this) as MainWindow;
    if (parentWindow != null)
    {
        parentWindow.SomeHandler(sender, e);
    }
}

Note that this create a strong coupling between the control and the window.

Binding to a SwitchToABCCommand command in the control XAML also creates an indirect coupling to the view model. A better way would be to add a command property to the control and bind this one to the view model command property, eg:

<MyCustomControl YourCommand="{Binding SwitchToABCCommand }"  />