Sort one C# list by another

Question

I have 2 list objects, one is just a list of ints, the other is a list of objects but the objects has an ID property.

What i want to do is sort the list of objects by its ID in the same sort order as the list of ints.

Ive been playing around for a while now trying to get it working, so far no joy,

Here is what i have so far...

        //**************************
        //*** Randomize the list ***
        //**************************
        if (Session["SearchResultsOrder"] != null)
        {
            // save the session as a int list
            List<int> IDList = new List<int>((List<int>)Session["SearchResultsOrder"]);
            // the saved list session exists, make sure the list is orded by this
            foreach(var i in IDList)
            {
                SearchData.ReturnedSearchedMembers.OrderBy(x => x.ID == i);
            }
        }
        else
        {
            // before any sorts randomize the results - this mixes it up a bit as before it would order the results by member registration date                        
            List<Member> RandomList = new List<Member>(SearchData.ReturnedSearchedMembers);
            SearchData.ReturnedSearchedMembers = GloballyAvailableMethods.RandomizeGenericList<Member>(RandomList, RandomList.Count).ToList();

            // save the order of these results so they can be restored back during postback
            List<int> SearchResultsOrder = new List<int>();
            SearchData.ReturnedSearchedMembers.ForEach(x => SearchResultsOrder.Add(x.ID));
            Session["SearchResultsOrder"] = SearchResultsOrder;
        }   

The whole point of this is so when a user searches for members, initially they display in a random order, then if they click page 2, they remain in that order and the next 20 results display.

I have been reading about the ICompare i can use as a parameter in the Linq.OrderBy clause, but i can’t find any simple examples.

I’m hoping for an elegant, very simple LINQ style solution, well I can always hope.

Any help is most appreciated

Truegilly

Answer 1

One way of doing it:

List<int>  order = ....;
List<Item> items = ....;

Dictionary<int,Item> d = items.ToDictionary(x => x.ID);

List<Item> ordered = order.Select(i => d[i]).ToList();

Answer 2

Another LINQ-approach:

 var orderedByIDList = from i in ids 
                       join o in objectsWithIDs
                       on i equals o.ID
                       select o;