Q:

c# mongodb case sensitive search

I have a collection in which I store Email and password of user.
I obviously don't want to require the user to insert his email case sensitive and to be exactly as when he first registered.
I'm using mongodb 2.0 c# driver, I'm repeating it because I saw solutions to queries written with regex but I'm afraid I cant user it in here.
my query looks like 
var filter = Builders<ME_User>.Filter.And(
                                 Builders<ME_User>.Filter.Eq(u => u.Email, email),
                                 Builders<ME_User>.Filter.Eq(u => u.Password, password));
            ME_User foundUser = null;
            var options = new FindOptions<ME_User>
            {
                Limit = 1
            };
            using (var cursor = await manager.User.FindAsync(filter, options))
            {
                while (await cursor.MoveNextAsync())
                {
                    var batch = cursor.Current;
                    foreach (ME_User user in batch)
                        foundUser = user;
                }
            }

I have an issue with disorder, kill me, but I cant allow myself save this data again with lower case and have 2 copies of the same thing. Also, I want the email to be saved EXACTLY like the user inserted it.

A:

Filtering on string fields in Mongodb is case sensitive without using regular expressions. Why exactly you cannot use regular expressions?
Your query can be edited like this:
var filter = Builders<ME_User>.Filter.And(
Builders<ME_User>.Filter.Regex(u => u.Email, new BsonRegularExpression("/^" + email + "$/i"), 
Builders<ME_User>.Filter.Eq(u => u.Password, password));

Notice the "^" and "$" signs to specify a complete word search and most important the case-insensitive operator at the end of the regular expression ("/i").
Another way vould be the Text search, that requires the creation of a text index and is case insensitive for latin alphabet: http://docs.mongodb.org/manual/reference/operator/query/text/#match-operation
In C#, you will use with the Text Filter:
var filter = Builders<ME_User>.Filter.And(
Builders<ME_User>.Filter.Text(email), 
Builders<ME_User>.Filter.Eq(u => u.Password, password));

With a text index query in an OR clause, you will need to create an index on Password field as well, otherwise the OR query will produce an error:

Other non-TEXT clauses under OR have to be indexed as well

A:

I'd prefer using Linq.
var match = theCollection.AsQueryable().SingleOrDefault(x =>
    x.Email.ToLower() == emailToSearchFor.ToLower());

