Question

I have a Collection of type string that can contain any number of elements.

Now i need to find out all those elements that are duplicating and find out only the first occurance of duplicating elements and delete rest.

For ex

 public class CollectionCategoryTitle
    {
        public long CollectionTitleId { get; set; }
        public bool CollectionTitleIdSpecified { get; set; }
        public string SortOrder { get; set; }
        public TitlePerformance performanceField { get; set; }      
        public string NewOrder { get; set; }    
    }

    List<CollectionCategoryTitle> reorderTitles = 
        (List<CollectionCategoryTitle>)json_serializer
            .Deserialize<List<CollectionCategoryTitle>>(rTitles);

Now i need to process this collection in such a way tat it removes duplicates but it must keep the 1st occurance.

EDIT:

I have updated the code and i need to compare on “NewOrder ” property

Thanks

Answer 1

For your specific case:

var withoutDuplicates = reorderTitles.GroupBy(z => z.NewOrder).Select(z => z.First()).ToList();

For the more general case, Distinct() is generally preferable. For example:

        List<int> a = new List<int>();
        a.Add(4);
        a.Add(1);
        a.Add(2);
        a.Add(2);
        a.Add(4);

        a = a.Distinct().ToList();

will return 4, 1, 2. Note that Distinct doesn’t guarantee the order of the returned data (the current implementation does seem to return them based on the order of the original data – but that is undocumented and thus shouldn’t be relied upon).