/**
* Creates a GridFS instance for the specified bucket
* in the given database.
*
* @param db database to work with
* @param bucket bucket to use in the given database
*/
public GridFS(DB db, string bucket)
{
_db = db;
_bucketName = bucket;
_filesCollection = _db.getCollection(_bucketName + ".files");
_chunkCollection = _db.getCollection(_bucketName + ".chunks");
_chunkCollection.ensureIndex(BasicDBObjectBuilder.start().Add("files_id", 1).Add("n", 1).get());
_filesCollection.setObjectClass(typeof(GridFSDBFile));
}