Build query with C# mongo driver

Question

I wonder how to build complex query using mongo driver. This is my query:

var builder = Builders<MongoNavFilter>.Filter;
var query = builder.Where(x => x.Link == link && x.SubLink == subLink);
if (some statement)
{
    var finalExpression = ...
    query = query & Builders<MongoNavFilter>.Filter.Where(finalExpression); 
}
if (onsale)
    query = query & Builders<MongoNavFilter>.Filter.Where(x => !(x.Promo == null && x.Promo == string.Empty));

var filters = _db.GetCollection<MongoNavFilter>("NavFilters").
                    Find(query).ToList();

With EF IQueryable this code is working fine, but I can't build correct query with mongo driver. Could anyone told me what am I doing wrong?

Answer 1

Knowing what the finalExpression is would help, in case the problem is there. In my opinion, there might be a problem with mongodb driver's translation of !(x.Promo == null && x.Promo == string.Empty)

Could you try the following code instead of yours and see if it will make a difference

var builder = Builders<MongoNavFilter>.Filter;
var query = builder.Eq(x => x.Link, link) & builder.Eq(x=> x.SubLink, subLink);
if (some statement)
{
    var finalExpression = ... // write this using the same syntax 
    query = query & filter; 
}
if (onsale)
    query = query & builder.Ne(x=>x.Promo, null) & builder.Ne(x=> x. Promo, string.Empty);

var filters = _db.GetCollection<MongoNavFilter>("NavFilters").
                Find(query).ToList();