I have a list of objects of type }
I need to sort the list of
Can I do this dynamically.
Please help.
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Based on your below comments it sounds very likely that you are not correctly populating your properties. Your core issue is probably not with the ordering. If you want an answer to your question you need to post the code that sets your properties.Michael Richardson– Michael Richardson2013-11-18 05:09:57 +00:00Commented Nov 18, 2013 at 5:09
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2 Answers
LINQ has OrderBy / OrderByDescending methods which make this type of sorting trivial e.g.
var orderByBookingRef = listOfRestaurants.OrderBy(x => x.Booking.BookingRef);
var orderByLatestBooking = listOfRestaurants.OrderByDescending(x => x.Booking.BookingDateTime);
var orderByLatestReview = listOfRestaurants.OrderByDescending(x => x.RestReview.ReviewDate);
The above is known as Lambda expressions which are a bit better in terms of readability, if you prefer pure LINQ syntax
var orderByBookingRef = from r in listOfRestaurants
orderby r.Booking.BookingRef
select r;
var orderByLatestBooking = from r in listOfRestaurants
orderby r.Booking.BookingDateTime descending
select r;
var orderByLatestReview = from r in listOfRestaurants
orderby r.RestReview.ReviewDate descending
select r;
6 Comments
user2921973
Hi James Thank you for your reply. I already tried the first solution (lambda expression.) I get this error "Check to determine if the object is null before calling the method." I used istOfRestaurants.OrderBy(x => x.Booking.BookingRef); the above mentioned error is coming because X has all the objects (Booking, Restaurant and RestaurantReview) as null. Don't know why.
user2921973
Hi James Thank you for your reply. I already tried the first solution (lambda expression.) I get this error "Check to determine if the object is null before calling the method." I used istOfRestaurants.OrderBy(x => x.Booking.BookingRef); the above mentioned error is coming because X has all the objects (Booking, Restaurant and RestaurantReview) as null. Tried the LINQ expression, gives same error.
user2921973
Actually my aim was to do it dynamically by constructing the sort expression. but even the basic lambda is not working.
Michael Richardson
If the objects are null, then you're probably doing something wrong. Can you post the code that instantiates the objects and tries to do the sorting?
James
@user2921973 You have plagued this thread with unnecessary code, if you want to show example code edit your original question. Also, if the inner classes are
null then clearly they aren't being set. Update your question with some example code which reproduces the problem and it might make the issue a bit clearer. |
And the other form of linq:
var sorted_by_prop =
from some_object in list_of_rest
orderby some_object.prop_name_here descending // or ignore descending if you don't want it descending
select some_object;
Specific case, assuming your list is called MyList, by Restaurant.RestaurantId field:
var sorted_list =
from rest in MyList
orderby rest.Restaurant.RestaurantId
select rest;
Will return the list by the Id of the restaurant, ascending
As per comment: You can do
var sorted_list =
from rest in MyList
where rest.Booking != null && // same for the rest
orderby rest.Restaurant.RestaurantId
select rest;
this way it'll skip the ones that are null ...
1 Comment
user2921973
Thanks Noctis, I get this error "Check to determine if the object is null before calling the method. use the new keyword to create an object instance" var sorted_list = from rest in listR orderby rest.Restaurant.RestaurantId select rest; the above mentioned error is coming because rest has all the objects (Booking, Restaurant and RestaurantReview) as null. Though original listR has all objects correctly populated
