Question 184981 in ASP.NET Question posted in
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Asp.net – Remove adjacent duplicates in List C#

I have a below list and i need to remove adjacent duplicate item only.

Sample List

var data = new List<NewsModel>
            {
                new NewsModel { ID = 1, Name = "AAA" },
                new NewsModel { ID = 2, Name = "AAA" },
                new NewsModel { ID = 3, Name = "BBB" },
                new NewsModel { ID = 4, Name = "CCC" },
                new NewsModel { ID = 5, Name = "CCC" },
                new NewsModel { ID = 6, Name = "AAA" },
                new NewsModel { ID = 7, Name = "DDD" },
                new NewsModel { ID = 8, Name = "DDD" },
                new NewsModel { ID = 9, Name = "CCC" }

            };

Expected Result

    var data = new List<NewsModel>
        {
            new NewsModel { ID = 1, Name = "AAA" },
            new NewsModel { ID = 2, Name = "BBB" },
            new NewsModel { ID = 3, Name = "CCC" },
            new NewsModel { ID = 4, Name = "AAA" },
            new NewsModel { ID = 5, Name = "DDD" },
            new NewsModel { ID = 6, Name = "CCC" }

        };

I have tried it like below,But it’s not came as expected result..

    foreach (var item in NewsModel.ToList())
                {
                    if (NewsModel.Count() >= NewsModel.IndexOf(item) + 1)
                    {

                            _nextItem = NewsModel[NewsModel.IndexOf(item) + 1];

                            if (item.Name == _nextItem.Name)
                            {

                                NewsModel.Remove(item);

                            }
                    }
                }
Tags:

3

Answers


  1. 0

    This will remove all adjacent entries that are equal.

    for (int i = 0; i < data.Count-1; i++)
{
    if (data[i].Name == data[i+1].Name)
    {
        data.RemoveAt(i);
        i--;
    }
}

    EDIT

    I missed that you want the ID’s to be updated by the end.
    Do another for loop after the first one I sent, that does this

    for (int i = 0; i < data.Count; i++)
    data[i].ID = i + 1;
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  2. 0

    There are several methods. I wrote two methods(linq,iterator)

    Linq

    You can use Linq to create List without duplicates adjacent and can generate new Id with Index in Select

    data = data
            .Where((x, i) => i == 0 || x.Name != data[i - 1].Name)
            .Select((r, index) => new { ID = index + 1, Name = r.Name }).ToList();

    Result

    ID Name
    1 AAA
    2 BBB
    3 CCC
    4 AAA
    5 DDD
    6 CCC

    iterator

    use

    data = Common.RemoveAdjecentDuplicates(data);

    Classes

    public static class Common
{
    internal static IEnumerable<NewsModel> RemoveAdjecentDuplicates(IEnumerable<NewsModel> newsModel)
    {
        using (var iterator = newsModel.GetEnumerator())
        {
            if (!iterator.MoveNext()) yield break;

            var current = iterator.Current;
            int Index = 1;
            yield return new NewsModel() { Name = current.Name, ID = Index };

            while (iterator.MoveNext())
            {
                if (iterator.Current.Name.Equals(current.Name)) continue;
                current = iterator.Current;
                Index++;
                yield return new NewsModel() { Name = current.Name, ID = Index };
            }
        }
    }


}
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  3. 0

    Hum, the re-numbering of the ID is a bit of monkey wrench.

    So, this:

            var data = new List<NewsModel>
        {
            new NewsModel { ID = 1, Name = "AAA" },
            new NewsModel { ID = 2, Name = "AAA" },
            new NewsModel { ID = 3, Name = "BBB" },
            new NewsModel { ID = 4, Name = "CCC" },
            new NewsModel { ID = 5, Name = "CCC" },
            new NewsModel { ID = 6, Name = "AAA" },
            new NewsModel { ID = 7, Name = "DDD" },
            new NewsModel { ID = 8, Name = "DDD" },
            new NewsModel { ID = 9, Name = "CCC" }

        };

        var data2 = new List<NewsModel>();
        int iID = 0;
        string sPrevious = "";
        for (int j = 0; j < data.Count;j++)
        {
            NewsModel OneNews = data[j];
            if (sPrevious != OneNews.Name)
            {
                iID++;
                OneNews.ID = iID;
                data2.Add(OneNews);
                sPrevious= OneNews.Name;    
            }
        }

        foreach(NewsModel OneNews in data2)
            Debug.Print($"ID = {OneNews.ID}, Name = {OneNews.Name}");

    Output:

    ID = 1, Name = AAA
ID = 2, Name = BBB
ID = 3, Name = CCC
ID = 4, Name = AAA
ID = 5, Name = DDD
ID = 6, Name = CCC

    Tough call if your requiring is to "in place" remove from existing list, or as the above does, and creates a new list.

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