How to remove duplicate record using linq?

Question

I have list of list and want to remove duplicate from list. Data is stored in list format say IEnumerable<IEnumerable<string>> tableData if we consider it as table value, parent list is for rows and child list is values of every column. Now I want to delete all duplicate rows. from below table value A is duplicate.

List<List<string>> ls = new List<List<string>>();
ls.Add(new List<string>() { "1", "A" });
ls.Add(new List<string>() { "2", "B" });
ls.Add(new List<string>() { "3", "C" });
ls.Add(new List<string>() { "4", "A" });
ls.Add(new List<string>() { "5", "A" });
ls.Add(new List<string>() { "6", "D" });
IEnumerable<IEnumerable<string>> tableData = ls;

var abc = tableData.SelectMany(p => p).Distinct();   ///not work

after operation, I want abc should be exactly tableData format

ls.Add(new List<string>() { "1", "A" });
ls.Add(new List<string>() { "2", "B" });
ls.Add(new List<string>() { "3", "C" });   
ls.Add(new List<string>() { "6", "D" });

What is PropertyData? It would really help if you'd show a short but complete program demonstrating what your data looks like. — Jon Skeet
– Jon Skeet, Commented Jun 3, 2014 at 10:11
IEnumerable<IEnumerable<PropertyData>> tableData contains complete table.where each parent list as row and each child list as columns for that row. — Sam
– Sam, Commented Jun 3, 2014 at 10:15
It's still unclear what you've got, to be honest. A short but complete example would be much clearer. — Jon Skeet
– Jon Skeet, Commented Jun 3, 2014 at 10:21

Dialecticus · Accepted Answer · 2014-06-03 12:01:35Z

3

tableData.GroupBy(q => q.Skip(1).First()).Select(q => q.First())

edited Jun 3, 2014 at 12:01

answered Jun 3, 2014 at 11:22

Dialecticus

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Comments

DGibbs · Accepted Answer · 2014-06-03 10:39:48Z

2

You can use the overload of Distinct passing in an IEqualityComparer assuming you actually have an IEnumerable<IEnumerable<PropertyData>>.

For example:

var items = tableData.SelectMany(x => x).Distinct(new TableComparer());

And the comparer:

public class TableComparer : IEqualityComparer<PropertyData>
{
    public bool Equals(PropertyData x, PropertyData y)
    {
        return x.id == y.id;
    }

    public int GetHashCode(PropertyData pData)
    {
        return pData.id.GetHashCode();
    }
}

If it's just an IEnumerable<IEnumerable<string>>, you can use Distinct() without the overload:

var items = tableData.SelectMany(x => x).Distinct();

Though your question lacks clarity..

answered Jun 3, 2014 at 10:39

DGibbs

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Comments

Philip Pittle · Accepted Answer · 2014-06-03 10:23:18Z

0

var distinctValues = tableData.SelectMany(x => x).Distinct();

This will flatten your list of lists and select the distinct set of strings.

answered Jun 3, 2014 at 10:23

Philip Pittle

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Comments

Dhaval Patel · Accepted Answer · 2014-06-03 10:28:17Z

0

you can use below menioned code

         List<List<string>> ls=new List<List<string>>();
         ls.Add(new List<string>(){"Hello"});
         ls.Add(new List<string>(){"Hello"});
         ls.Add(new List<string>() { "He" });
         IEnumerable<IEnumerable<string>> tableData = ls;
         var abc = tableData.SelectMany(p => p).Distinct();

O/P is

Hello

He

answered Jun 3, 2014 at 10:28

Dhaval Patel

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3 Comments

Dhaval Patel Over a year ago

var abc = tableData.Select(q => q.ElementAt(1).Distinct());

Dialecticus Over a year ago

No, that's not it either.

Sam Over a year ago

No, It doesn't work. It will not give distinct record.

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