Build this LEFT() "SQL" in MongoDB Query?

Have an BsonDocument collection with PhoneNumber in the "1234567890" format. This SQL gets all the PhoneNumbers with the Area Codes between 300 and 399;

WHERE (LEFT(PhoneNumber,3) BETWEEN '300' AND '399') 

How wo开发者_开发知识库uld I do this in MongoDB? I would like to use the MongoDB.Driver.Builders if possible.

If you just want phone number that's starts from number '3' you can just use smart decision of @mstearn, here just c# realization:

var query = Query.EQ("PhoneNumber", new BsonRegularExpression("^3"));

But lets say if you need query first 3 numbers in range 345 -- 369 to make it work (without slow operators: $where, $regex) you can create additional field and store there first 3 numbers (area code) of phone. And then use query proposed by @yi_H , here again c# driver realization:

var query = Query.GTE("PhoneAreaCode", 345).LTE(369);

Don't care about extra field in mongodb -- it's common practice. Extra fields usual working faster than any calculation during querying.

{'PhoneNumber': {'$gte': '300', '$lt': '400'}}

{'PhoneNumber': /^3/ } or {'PhoneNumber': {'$regex': '^3'}}