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

The unique index only needs to be created once, after that any document inserts that contain a duplicate email address will fail. Here's an example:

var server = MongoServer.Create("mongodb://localhost");
var db = server.GetDatabase("myapp");

var users = db.GetCollection("users");

users.EnsureIndex(new IndexKeysBuilder()
    .Ascending("EmailAddress"), IndexOptions.SetUnique(true));

var user1 = new User { EmailAddress = "joe@example.com" };
var user2 = new User { EmailAddress = "joe@example.com" };

try
{
    users.Save(user1, WriteConcern.Acknowledged);
    users.Save(user2, WriteConcern.Acknowledged);  // <-- throws MongoSafeModeException
}
catch (MongoSafeModeException ex)
{
    Console.WriteLine(ex.Message);
}