Creating MongoDB Unique Key with C#

Question

I am fighting to create a unique field EmailAddress. I\'ve already seen in forums that I have to create an index, but it didn\'t work out for me so far. Does an

Answer 1

Your code looks right. Here's a full running program for you to compare against:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Builders;

namespace TestEnsureIndexOnEmailAddress {
    public class User {
        public ObjectId Id;
        public string FirstName;
        public string LastName;
        public string EmailAddress;
    }

    public static class Program {
        public static void Main(string[] args) {
            var server = MongoServer.Create("mongodb://localhost/?safe=true");
            var database = server["test"];
            var users = database.GetCollection("users");
            if (users.Exists()) { users.Drop(); }

            users.EnsureIndex(IndexKeys.Ascending("EmailAddress"), IndexOptions.SetUnique(true));
            var john = new User { FirstName = "John", LastName = "Smith", EmailAddress = "jsmith@xyz.com" };
            users.Insert(john);
            var joe = new User { FirstName = "Joe", LastName = "Smith", EmailAddress = "jsmith@xyz.com" };
            users.Insert(joe); // should throw exception
        }
    }
}

You can also use the mongo shell to confirm that the index got created:

> db.users.getIndexes()
[
        {
                "name" : "_id_",
                "ns" : "test.users",
                "key" : {
                        "_id" : 1
                },
                "v" : 0
        },
        {
                "_id" : ObjectId("4de8152ee447ad2550e3b5fd"),
                "name" : "EmailAddress_1",
                "ns" : "test.users",
                "key" : {
                        "EmailAddress" : 1
                },
                "unique" : true,
                "v" : 0
        }
]
>