public SelectedSnapshot Map(DbDataReader reader)
{
var persistenceId = reader.GetString(0);
var sequenceNr = reader.GetInt64(1);
var timestamp = new DateTime(reader.GetInt64(2));
var metadata = new SnapshotMetadata(persistenceId, sequenceNr, timestamp);
var snapshot = GetSnapshot(reader);
return new SelectedSnapshot(metadata, snapshot);
}