System.Windows.Controls.AutoCompleteBox.HasFocus C# (CSharp) Method

        protected bool HasFocus()
        {
            DependencyObject focused =
#if SILVERLIGHT
                FocusManager.GetFocusedElement() as DependencyObject;
#else
                // For WPF, check if the element that has focus is within the control, as
                // FocusManager.GetFocusedElement(this) will return null in such a case.
                IsKeyboardFocusWithin ? Keyboard.FocusedElement as DependencyObject : FocusManager.GetFocusedElement(this) as DependencyObject;
#endif
            while(focused != null)
            {
                if(ReferenceEquals(focused, this))
                {
                    return true;
                }

                // This helps deal with popups that may not be in the same 
                // visual tree
                DependencyObject parent = VisualTreeHelper.GetParent(focused);
                if(parent == null)
                {
                    // Try the logical parent.
                    FrameworkElement element = focused as FrameworkElement;
                    if(element != null)
                    {
                        parent = element.Parent;
                    }
                }
                focused = parent;
            }
            return false;
        }