Remove duplicate rows mvc

Question

I have this method

Meeting is a class
Attendees is an ICollection in Meeting

Class

public partial class Meeting
    {

        public Meeting()
        {
            this.Attendees = new List<Attendees>();
        }

public virtual ICollection<Attendees> Attendees{ get; set; }
[...]

Method Controller

private void RemoveRowsDuplicated(Meeting model)
        {
            if (model.Attendees != null)
            {
                foreach (var item in model.Attendees.GroupBy(x => x.UserName).Select(y => y.Last()))
                {
                    context.Attendees.Remove(item);
                }
            }
        }

The objective is remove duplicate Attendees with the same username in the table.
But the current method it deletes all records and keeps the duplicate
Where am I going wrong?

I believe, it was already answered here: http://stackoverflow.com/questions/1606679/remove-duplicates-in-the-list-using-linq — drcolombo, Jan 14 '16 at 15:50

Mitklantekutli · Accepted Answer · 2016-01-14T15:43:07.730

Correct version of your method will look like this:

private static void RemoveRowsDuplicated(Meeting model)
        {
            if (model.Attendees != null)
            {
                var duplicates = new List<Attendees>();
                foreach (var item in model.Attendees.GroupBy(x => x.UserName).Where(x=>x.Count()>1))
                {
                    duplicates.AddRange(item.Skip(1));
                }
                duplicates.ForEach(x=>context.Attendees.Remove(x));
            }
        }

score 0 · Answer 2 · answered Jan 14 '16 at 15:43

0

You can try writing raw SQL and invoking via EF and return Attendees objects in a list.

var query = "Select * from Attendees group by username";
var attendeesList = dbContext.Database.SqlQuery<Attendees>(query).ToList<Attendees>();

answered Jan 14 '16 at 15:43

jamdownian

410
3
11

AntonE · Answer 3 · 2016-01-14T15:47:12.323

As I can see you grouped elements by name and remove last item. So you remove unique elements. Like this

 private void RemoveRowsDuplicated(Meeting model)
        {
             if (model.Attendees != null)
             {
                var temporaryAtendees = new List<Attendees>();
                foreach(var item in model.Attendees)
                {
                    if (temporaryAtendees.Contains(item))
                    {
                        context.Attendees.Remove(item);
                    }
                    else
                    {
                        temporaryAtendees.Add(item);
                    }
                }
                }
            }

Yes I see now you have other question and my answer not about this — AntonE, Jan 14 '16 at 15:39

Remove duplicate rows mvc

3 Answers3