Hi Le Thien Hoang,
MediaElement seems can not directly play the Youtube link. You will get a error message once you apply the source directly to the MediaElement: MF_MEDIA_ENGINE_ERR_SRC_NOT_SUPPORTED : HRESULT - 0xC00D36C4
I would suggest you to set a MediaElement_MediaFailed event to see what is the exactly error message. And you are using DataModel.YoutubeVideo which is not a original Windows Store App API, maybe he did some URI convert somewhere in the code, for this reason,
you may ask code owner why the youtube cannot be played in Windows Store App.
--James
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Thanks
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