How to create indexes in MongoDB via .NET

Question

I've programmatically created a new document collection using the MongoDB C# driver.

At this point I want to create and build indexes programmatically. How can I do that?

Answer 1

you should use CreateIndex as EnsureIndex is marked obsolete for future compatibility with the next versions of MongoDB:

var client = new MongoClient("mongodb://localhost");
var db = client.GetServer().GetDatabase("db");
var collection = db.GetCollection<Hamster>("Hamsters");

collection.CreateIndex(IndexKeys<Hamster>.Ascending(_ => _.Name));

Answer 2

The overload of CreateOneAsync in the currently accepted answer is now marked as obsolete with the message "Use CreateOneAsync with a CreateIndexModel instead." Here's how you do it:

static async Task CreateIndex(string connectionString)
{
    var client = new MongoClient(connectionString);
    var database = client.GetDatabase("HamsterSchool");
    var collection = database.GetCollection<Hamster>("Hamsters");
    var indexOptions = new CreateIndexOptions();
    var indexKeys = Builders<Hamster>.IndexKeys.Ascending(hamster => hamster.Name);
    var indexModel = new CreateIndexModel<Hamster>(indexKeys, indexOptions);
    await collection.Indexes.CreateOneAsync(indexModel);
}

Answer 3

Something like this should do:

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

var users = db.GetCollection<User>("users");

users.EnsureIndex(new IndexKeysBuilder().Ascending("EmailAddress"));

Please see the following bits in the documentation:

• http://api.mongodb.org/csharp/current/html/06bcd201-8844-3df5-d170-15f2b423675c.htm