CODEWITHSUNDEEP
mongodbmongodb-.net-driver
Daniele Tassone
Daniele Tassone

Reputation: 2174

Get only a specified field in MongoDB with C#

first time i'm using MongoDB.

I have read this example:

SELECT a,b FROM users WHERE age=33 db.users.find({age:33}, {a:1,b:1})

But I can't translate it into C#. Can anyone help me?

Upvotes: 28

Views: 41022

Answers (4)

Andrew Orsich
Andrew Orsich

Reputation: 53685

You can do it using SetFields method of MongoCursor class, below full example:

var server = MongoServer.Create(connectionString);
var db = _server.GetDatabase("dbName");
var users = db.GetCollection("users");

var cursor = users.FindAs<DocType>(Query.EQ("age", 33));
cursor.SetFields(Fields.Include("a", "b"));
var items = cursor.ToList();

Upvotes: 26

adi ben
adi ben

Reputation: 489

//create user class
//(not sure how your class looks like)

public class User
{

public int age;

public string a;

public string b;
}

//then you can use LINQ easily

var server = MongoServer.Create(connectionString);
var db = server.GetDatabase("dbName");
var usersCollection = db.GetCollection<User>("users");

var filteredCollection = usersCollection.AsQueryable().Where(x=> x.age < 33).Where(x=> x.a != null).Contains(x=> x.b != null);

Upvotes: 3

IsraelKo
IsraelKo

Reputation: 116

you can use anonymous class

    public class User
    {
        public int age;
        public string  a;
        public string  b;
    }

    var collection = db.GetCollection<User>("Users");
    var results = collection.Find(Builders<User>.Filter.Eq(user => user.age, 33))
            .Project(u => new { u.a, u.b }).ToList();

Upvotes: 6

Heo Đất Hades
Heo Đất Hades

Reputation: 1633

I have translated your query below using the new C# driver (2.2)

var mongoClient = new MongoClient(""mongodb://127.0.0.1:27017"");
var database = mongoClient.GetDatabase("databaseName");
IMongoCollection<Users> _collection = database.GetCollection<Users>("Users");
var condition = Builders<Users>.Filter.Eq(p => p.age, 33);
var fields = Builders<Users>.Projection.Include(p => p.a).Include(p => p.b);
var results= _collection.Find(condition).Project<Users>(fields).ToList().AsQueryable();

Upvotes: 35

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