Filter record in MongoDB using Asp.net

using MongoDB.Bson;

using MongoDB.Driver;              

                         

static MongoClient client = new MongoClient("mongodb://localhost:27017"); //Set the connection string

static IMongoDatabase db = client.GetDatabase("test"); //Database name

public void ListOne(string age)

 {

    IMongoCollection<BsonDocument> collection = db.GetCollection<BsonDocument>("user");

    var filter = Builders<BsonDocument>.Filter.Eq("age", age);

    var res = collection.Find(filter).ToList();

 }