Tutorial :Get the Thumb of a Slider



Question:

I'm just trying to figure out a way to get the thumb of a slider in WPF, something like so:

Slider mySlider = new Slider();    Thumb thumb = slider.Thumb;  

Now I know it's not possible as simple as this; but there must be a work around this. Let me know if you know any.

Thanks!


Solution:1

Slider has a TemplatePartAttribute that declares it should have a template part called PART_Track of type Track. The Track can give us a reference to the Thumb. Keep in mind that it's possible to give the Slider a template with no Track, in which case there will be no Thumb.

private static Thumb GetThumb(Slider slider)  {      var track = slider.Template.FindName("PART_Track", slider) as Track;      return track == null ? null : track.Thumb;  }  


Solution:2

Found the solution on my own, with a little help from the VisualTreeHelper. Any optimization greatly appreciated:

private Thumb Thumb  {      get      {          return GetThumb(this /* the slider */ ) as Thumb;;      }  }    private DependencyObject GetThumb(DependencyObject root)  {      if (root is Thumb)          return root;        DependencyObject thumb = null;        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(root); i++)      {          thumb = GetThumb(VisualTreeHelper.GetChild(root, i));            if (thumb is Thumb)              return thumb;      }        return thumb;  }  


Solution:3

If you just want to add an event handler to the thumb and don't want to wait or force rendering to avoid slider.Template being null, you can do something like this:

slider.AddHandler(Thumb.DragStartedEvent, new DragStartedEventHandler((sender, e) =>  {      // Handling code  }));  

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