Question

I have some thing like this

SecuritySearcher sc = new SecuritySearcher();
Dictionary<string, bool> groupsMap = 
    sc.GetUserGroupMappings(domainName, currentUser, distGroups.ToList());

IQueryable<HotelTravel> groupq = 
    (from hotel in qHs
    join hp in qHps on hotel.HotelTravelId equals hp.HotelTravelId
    where !string.IsNullOrEmpty(hp.GroupName)
       && groupsMap.ContainsKey(hp.GroupName) 
       && groupsMap[hp.GroupName] == true
    select hotel);

While executing Linq statement it is throwing exception saying
LINQ to Entities does not recognize the method ‘Boolean ContainsKey(System.String)’ method, and this method cannot be translated into a store expression.

Answer 1

In order to translate your expression into a database query, the database would somehow have to know the contents of your dictionary and have a way to access it from the query. There is no dictionary mechanism in SQL, but that doesn’t matter because you don’t need a dictionary because you’re just looking for keys whose value is a certain constant. You can turn that set of keys into a list and see if that list contains what you’re looking for:

var groupsList = (from kvp in groupsMap     // find all keys in groupsMap
                  where kvp.Value == true   // where the value is set to True
                  select kvp.Key).ToList();

IQueryable<HotelTravel> groupq =
    from hotel in qHs
    join hp in qHps on hotel.HotelTravelId equals hp.HotelTravelId
    where !string.IsNullOrEmpty(hp.GroupName)
          && groupsList.Contains(hp.GroupName)
    select hotel;

I suspect that you don’t actually have the empty string as a key in your dictionary, though, which means you can get rid of the IsNullOrEmpty call and just have where groupsList.Contains(hp.GroupName).