从主窗口进行内容控制中的访问控制

Question

I had found methods to access main window from usercontrol:

• Window parentWindow = Window.GetWindow(this);
• DependencyObject parentWindow = VisualTreeHelper.GetParent(child);
• Application.Current.MainWindow as parentWindow;

I have some questions:

1. Which of the above methods is the best?
2. How can I access control in usercontrol from Main Window and from usercontrol to usercontrol in the same Main Window?

Thanks, Skip for my bad English :)

Answer 1

Current.MainWindow is ideal in every case because if a UserControl is embedded inside another UserControl , you can still use Current.MainWindow traversing up the tree. All the methods are fine and it all depends on usage and what you're trying to accomplish.

To access a control (lets say TextBlock ) inside a UserControl .

TextBlock tb = FindVisualChildren<TextBlock>(usercontrol)

public static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
{
    if (depObj != null)
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
            if (child != null && child is T)
            {
                yield return (T)child;
            }

            foreach (T childOfChild in FindVisualChildren<T>(child))
            {
                yield return childOfChild;
            }
        }
    }
}

Answer 2

None of the suggested is "best":

Application.Current.MainWindow or Window.GetWindow(this) : not good since you're breaking with common design patterns and rules (like "principle dependency inversion" or MVVM)

Using VisualTreeHelper is sometimes useful when coding XAML Converters (such elements that directly deal with the UI). Not preferrable in code since you're strongly depending on your xaml visual tree.

If you want to communicate between the MainWindow and a UserControl , keeping a resuable UserControl for other assemblies, add one or more dependency properties to your Usercontrol, and set the binding in Xaml.

If you want quick and easy test apps, sure Application.Current.MainWindow is still a good choice.