UpdateManyAsync() is the function in .net 4.5 and later versions for updating one or more number of records in MongoDB. It will also updates one record if your selection matches only one record

Example:

var updmanyresult = await collection.UpdateManyAsync(
                  Builders<BsonDocument>.Filter.Gt("MasterID", 100),
                  Builders<BsonDocument>.Update.Inc("MasterID", 10));