object wantedNode = grid.FindName("button");
    if (wantedNode is TextBlock)
    {
        // Following executed if Text element was found.
        TextBlock wantedChild = wantedNode as TextBlock;
        wantedChild.Background = Brushes.Blue;
    }

object wantedNode = grid.FindName("button");
    if (wantedNode is TextBlock)
    {
        // Following executed if Text element was found.
        TextBlock wantedChild = wantedNode as TextBlock;
        wantedChild.Background = Brushes.Blue;
    }