WPF User Control Parent

Question

I have a user control that I load into a main window at runtime. I cannot get a handle on the containing window from the user control.

I have tried this.Parent, but it's always null. Does anyone know how to get a handle to the containing window from a user control in WPF?

Here is how the control is loaded:

private void XMLLogViewer_MenuItem_Click(object sender, RoutedEventArgs e)
{
    MenuItem application = sender as MenuItem;
    string parameter = application.CommandParameter as string;
    string controlName = parameter;
    if (uxPanel.Children.Count == 0)
    {
     System.Runtime.Remoting.ObjectHandle instance = Activator.CreateInstance(Assembly.GetExecutingAssembly().FullName, controlName);
     UserControl control = instance.Unwrap() as UserControl;
     this.LoadControl(control);
    }
}

private void LoadControl(UserControl control)
{
    if (uxPanel.Children.Count > 0)
    {
     foreach (UIElement ctrl in uxPanel.Children)
     {
      if (ctrl.GetType() != control.GetType())
      {
       this.SetControl(control);
      }
     }
    }
    else
    {
     this.SetControl(control);
    }
}

private void SetControl(UserControl control)
{
    control.Width = uxPanel.Width;
    control.Height = uxPanel.Height;
    uxPanel.Children.Add(control);
}

Answer 1

Try using VisualTreeHelper.GetParent or use the bellow recursive function to find the parent window.

 public static Window FindParentWindow(DependencyObject child)
    {
        DependencyObject parent= VisualTreeHelper.GetParent(child);

        //CHeck if this is the end of the tree
        if (parent == null) return null;

        Window parentWindow = parent as Window;
        if (parentWindow != null)
        {
            return parentWindow;
        }
        else
        {
            //use recursion until it reaches a Window
            return FindParentWindow(parent);
        }
    }

Answer 2

Try using the following

Window parentWindow = Window.GetWindow(userControlRefernce);

The GetWindow method will walk the VisualTree for you and locate the window that is hosting your control.

Answer 3

I've found that the parent of a UserControl is always null in the constructor, but in any event handlers the parent is set correctly. I guess it must have something to do with the way the control tree is loaded. So to get around this you can just get the parent in the controls Loaded event.

For an example checkout this question http://stackoverflow.com/questions/296503/wpf-user-controls-datacontext-is-null

Answer 4

I needed to use the Window.GetWindow(this) method within Loaded event handler. In other words, I used both Ian Oakes' answer in combination with Alex's answer to get a user control's parent.

public MainView()
{
    InitializeComponent();

    this.Loaded += new RoutedEventHandler(MainView_Loaded);
}

void MainView_Loaded(object sender, RoutedEventArgs e)
{
    Window parentWindow = Window.GetWindow(this);

    ...
}

Answer 5

To all who observe that no parent can be found in the c'tor: It makes sense since the control is not parented yet. IOW, it's not stored in a parent yet.

Answer 6

I'll add my experience. Although using the Loaded event can do the job, I think it may be more suitable to override the OnInitialized method. Loaded occurs after the window is first displayed. OnInitialized gives you chance to make any changes, for example, add controls to the window before it is rendered.