public Task <Tuple <bool, long> > GetMetadataIDAsync(string hash, long size)
 {
     return(RunOnMain(() =>
     {
         long metadataid;
         var r = m_database.GetMetadatasetID(hash, size, out metadataid, m_transaction);
         return new Tuple <bool, long>(r, metadataid);
     }));
 }