public long GetCountByDate(DateTime?startTime, DateTime?endTime) { List <FilterDefinition <BsonDocument> > list = new List <FilterDefinition <BsonDocument> >(); if (startTime != null) { list.Add(FilterBuilder.Gte("CreateTime", startTime.Value)); } if (endTime != null) { list.Add(FilterBuilder.Lte("CreateTime", endTime.Value)); } if (list.Count == 0) { return(MongoCollection.EstimatedDocumentCount()); } return(MongoCollection.CountDocuments(FilterBuilder.And(list))); }