Saving and Retrieving Uri of selected Ringtone in Preferences

Hi

I have a ringtone selector that returns the Android.Net.Uri for the selected RingTone. I save it as a string in my Preferences but when i try to retrieve it

            string ringpicked = MyUtils.GetSetting("ring",3).ToString();
            Android.Net.Uri uri = (Android.Net.Uri)ringpicked;

I get parse error..

Any help and suggestions appreciated

Regards

M.R.