PropertyGrid Tab Navigation

Hi, Is there an easy way to make the tab key move to the next editor rather than out of the PropertyGrid altogether?

There isn't an *easy* way, but there is a way.  See the following thread:

http://www.mindscape.co.nz/forums/Thread.aspx?ThreadID=1367

(you will need to scroll down just past half way).  In particular see http://www.mindscape.co.nz/forums/Post.aspx?ThreadID=1367&PostID=3953, and Sean's complete sample at http://www.mindscape.co.nz/forums/Post.aspx?ThreadID=1367&PostID=3965.

How about intercepting Key.TAB in previewKeyDown and turning it into Key.Down. Is there a way to do that?

I don't think that can be done directly.  You can probably intercept Key.Tab in OnPreviewKeyDown (though WPF does give special handling to the Tab key so I could be wrong here), and mark it as handled.  You could then try raising an artificial KeyDown event to simulate a down arrow, but I am not sure how well this will work (I have a feeling WPF examines the keyboard state itself).  A more reliable approach is probably to call the same code the property grid does when it gets a cursor key.  Unfortunately this method is private but the code to replicate it is reasonably simple:

static void PerformCursorKeyNavigation(Key key)
{
  TreeViewItem tvitem = GetAncestorOfFocusedElement<TreeViewItem>();
  if (tvitem != null)
  {
    TraversalRequest tr = TraversalRequestFromNavigationKey(key, Keyboard.Modifiers);

    if (tr != null)
    {
      while (true)
      {
        UIElement element = Keyboard.FocusedElement as UIElement;
        if (element != null && element.IsDescendantOf(tvitem))
        {
          bool couldMove = element.MoveFocus(tr);
          if (!couldMove)
          {
            break;
          }
        }
        else
        {
          break;
        }
      }

      TreeViewItem newFocusedItem = GetAncestorOfFocusedElement<TreeViewItem>();
      if (newFocusedItem != null)
      {
        newFocusedItem.IsSelected = true;
      }
    }
  }
}

You would call this method, passing Key.Down as the key argument, from your tab interceptor.  Please note I have not tested this approach but this is how the grid internally handles arrow keys so it should work for you as well -- my concern would be more around whether tab can be intercepted successfully.

The helper functions for the navigation code are as follows:

static UIElement GetAncestor(UIElement from, Type ancestorType)
{
  if (ancestorType.IsInstanceOfType(from))
  {
    return from;
  }

  UIElement parent = VisualTreeHelper.GetParent(from) as UIElement;
  if (parent != null)
  {
    return GetAncestor(parent, ancestorType);
  }

  return null;
}

static T GetAncestorOfFocusedElement<T>() where T : UIElement
{
  return GetAncestor(Keyboard.FocusedElement as UIElement, typeof(T)) as T;
}

static TraversalRequest TraversalRequestFromNavigationKey(Key key, ModifierKeys modifiers)
{
  if (key == Key.Up && modifiers == ModifierKeys.None)
  {
    return new TraversalRequest(FocusNavigationDirection.Up);
  }
  if (key == Key.Down && modifiers == ModifierKeys.None)
  {
    return new TraversalRequest(FocusNavigationDirection.Down);
  }
  return null;
}

I have the same problem. All treads like "Sean's complete sample at http://www.mindscape.co.nz/forums/Post.aspx?ThreadID=1367&PostID=3965 " implements basic tab navigation.
Works good, but "Shift-Tab" does not select previous editor. Is there any way or example resolving this problem?