Load Image to a Mediafile varidabel using its address image path

Using media plugin we can get and store image to mediafile like this

private MediaFile _mediafile;  
_mediaFile = await CrossMedia.Current.PickPhotoAsync(new PickMediaOptions
        { 
        });

New the problem is How to get and load image to a mediafile using image path

private MediaFile _mediafile;  
_mediaFile =  "Image path from the device"