c# - open page to use navigation and token system to show a pdf file -

i have download 1 mupdf project pdfreader , have changes.

i stuck when click on list pdf file open return null navigation error.

when going place click on list working.my code , fileinfo property correct problem in _navigation.

please me...

 public void openfile(ifileinfo fileinfo)     {         if (isloading)             return;          _navigationservice.urifor<fileviewerpageviewmodel>().withparam(x => x.currentfileid, fileinfo.id).navigate();     }