track bar in media file using DirectShow lib in c#

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C#

directshow

hi,
i want to use a track bar in a window form which opens a media file as the video or audio plays i want to move the slider of the track bar accordingly . I had set all the properties of the track bar tool like maximun,minimun, trickfreguency small and large change accordingly.
using mediaposition i collect the currentPosition of the media and total duration using get_duration() method and sets the trackbar value to the current positin but the problem is as the media is running the slider of the bar is not moving .

plzzzz help me ASAP.