Multi-field queries using C# driver for MongoDB

Question

I'm having trouble figuring out syntax for what I'm trying to accomplish. As stated I'm using the C# driver for MongoDB.

I have a User entity defined as

[BsonIgnoreExtraElements]
public class User : MongoEntity
{
    [BsonElement]
    public string Username { get; set; }

    [BsonElement]
    public string Password { get; set; }

    [BsonElement]
    public string Email { get; set; }
}

I also have a UserService class that performs actions against the User collection in my mongo database. Below is an example of how i'm creating a real simple login example.

public UserPresentation Login(string username, string password)
{
    var entityQuery = Query<User>.EQ(e => e.Username, username.ToUpper());

    var entity = this.MongoConnectionHandler.MongoCollection.FindOne(entityQuery);

    return (entity != null && entity.Id.ToString().Length > 0 && entity.Password == password) ? new UserPresentation(entity) : null;
}

This works, however my question is... instead of creating a Query that only looks for Username == username, returning the element and then comparing the password in an if statement, can I somehow append more fields to the intial entityQuery object.

Query.And? Is that what you're looking for?

WiredPrairie
– WiredPrairie

2013-05-29 19:53:14 +00:00
Commented May 29, 2013 at 19:53 — WiredPrairie
– WiredPrairie, Commented May 29, 2013 at 19:53

davmos · Accepted Answer · 2013-05-29 21:28:22Z

14

You can use Query.And() like this...

var entityQuery = Query.And(
                      Query<User>.EQ(e => e.Username, username.ToUpper()),
                      Query<User>.EQ(e => e.Password, password)
                  );

See CSharp Driver Tutorial

Or you could do it LINQ style, see: CSharp Driver LINQ Tutorial

This is also interesting too: How to rewrite a MongoDB C# LINQ with a Projection Requirement using a MongoCursor

answered May 29, 2013 at 21:28

davmos

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2 Comments

Dylan Hayes Over a year ago

Nice I think the more LINQ approach is really what I was after from the beginning. I feel kind of dumb for not remembering how to do this, but perhaps this will save someone else a few minutes of poking around.

davmos Over a year ago

Don't feel dumb! :) As the popularity of MongoDB continues to grow, I'm sure it will help, so +1 for the question ;)

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