MongoDB C# Query Array of Objects that contain a property value

Question

My documents have an array property in them. Lets call it arrayProperty something like this:

 {
  _id: mongoObjectIdThingy,
  arrayProperty: [
    {string1:         


        

Answer 1

I believe you are looking for the In FilterDefinition, which would make your Builder look like this;

return Builders<MyObject>.Filter.ElemMatch(
            o => o.arrayProperty,
            Builders<ArrayProperty>.Filter.In(y => y.string1, listToFind));

This builds this query

db.MyObject.find({ "arrayProperty" : { "$elemMatch" : { "string1" : { "$in" : ["a", "b", "aString"] } } } })

To be able to use the Regex you would have to build a different query (I'm not on coffee so this is without any warranty)

        var listToFind = new List<string> { "a", "b", "astring" };

        var regexList = listToFind.Select(x => new BsonRegularExpression(x, "i"));

        var filterList = new List<FilterDefinition<MyObject>>();
        foreach (var bsonRegularExpression in regexList)
        {
            FilterDefinition<MyObject> fil = Builders<MyObject>.Filter.ElemMatch(o => o.arrayProperty, Builders<ArrayProperty>.Filter.Regex(
                 x => x.string1,
                 bsonRegularExpression));

            filterList.Add(fil);
        }


        var orFilter = Builders<MyObject>.Filter.Or(filterList);

        var result = collection.Find(orFilter).ToList();

Which builds the follow query

db.MyObject.find({ "$or" : [{ "arrayProperty" : { "$elemMatch" : { "string1" : /a/i } } }, { "arrayProperty" : { "$elemMatch" : { "string1" : /b/i } } }, { "arrayProperty" : { "$elemMatch" : { "string1" : /astring/i } } }] })