Question

I have two lists:

a. requestedAmenities 
b. units with amenities. 

I want to filter those units that have any one of the “requested amenities”.
I have tried to achieve the same result using foreach loops but I believe it should be much easier using LINQ. Can someone please help\advice?

UnitAmenities unitSearchRequestAmenities = unitSearchRequest.Amenities;

var exactMatchApartmentsFilteredByAmenities= new Units();
IEnumerable<string> requestAmenitiesIds =  unitSearchRequestAmenities.Select(element => element.ID);
foreach (var unitCounter in ExactMatchApartments)
{
    IEnumerable<string> unitAmenities = unitCounter.Amenities.Select(element => element.ID);

    foreach (var requestAmenityId in requestAmenitiesIds)
    {
        foreach (var unitAmenity in unitAmenities)
        {
            if (requestAmenityId == unitAmenity)
            {
                exactMatchApartmentsFilteredByAmenities.Add(unitCounter);
                //break to the outmost foreach loop
            }
        }
    }
}

Answer 1

You could filter based on compliance with an Intersect rule

var matchedAmenities = ExactMatchApartments.Where(ema => ema.Amenities
                                               .Any(x => unitSearchRequestAmenities
                                                   .Count(y => y.ID == x.ID) == 1));
exactMatchApartmentsFilteredByAmenities.AddRange(matchedAmenities);

This is a somewhat “custom” Intersect given that the default LINQ Intersect extension doesn’t support lambda expressions.