Mongo C# driver - Contains Filter

Question

I am using the latest version of Mongo C# driver which uses a lot of Async and builder pattern. Which is nice. I am trying to convert SQL where clauses into Mongo FilterDefinition object.

Any idea how to handle "contains"?
like:

where x contains 'ABC'

Solution 1

If x is a string, you could do so with a simple regex. For the 2.0 driver, you can manually create the FilterDefinition:

FilterDefinition<BsonDocument> filter = "{ x : { $regex : /ABC/ } }";

Or build the filter use the Builder:

var builder = Builders<BsonDocument>.Filter;
var filter = builder.Matches("x", "ABC");

Then you can use the filter in your query:

using (var cursor = await collection.Find(filter).ToCursorAsync())
{
    // ...
}

Solution 2

In order to achieve that in V2 API, use the `Filter.Regex':

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

var filter = Builders<BsonDocument>.Filter.Regex("fieldName", new BsonRegularExpression(".*fieldValue.*"));

var data = await (await coll.FindAsync<BsonDocument>(filter).ConfigureAwait(false)).ToListAsync();

//continue process data 

Solution 3

First, I highly recommend taking MongoDB University's .NET course (from Mongo itself). It's really thorough, and covers your question (and more) in depth.

Second, I assume that x is an array in your example.

MongoDB correctly handles polymorphism with arrays. If you have a class Post with an array of Tags, you can filter where Tag = ABC.

If you're using the C# linq methods, that looks like .Find(p => p.Tags == "ABC"). If you're using BsonDocument, that looks like new BsonDocument().Add("Tags", "ABC").

Solution 4

I was able to get this working using Filter.AnyIn like so

var filter = Builders<BsonDocument>.Filter.AnyIn("x", new List<string> { "ABC" });

This works if you're looking for multiple values too, just add them to the list.

View more solutions

Comments

[Mr767267]

Thanks! I am using 2.0 version of driver and could not .Matches() on Filter Builder, but I could find .Regex(), so I'll try with that.

[Yiannis P.]

Your builder method for the filter isn't correct. It cannot be Equal to since you're looking for Contains.