How remove items who is only one in List?

Question

5.00/5 (1 vote)

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Hi
I would like get data from list, which is used more time.
e.g. I have a list who contains items 1,2,5,2,8,7,8,2
I want only item who is more time 2,2,8,8,2

Is for this some method or?

I create my way this...
foreach and List.Contains and last step add to new List.

Thank you

Posted 26-Nov-14 22:45pm

smoula99

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5 solutions

Solution 5

Hello ,
Even Try The Following

C#

List<int> list = new List<int>() { 1, 3, 3, 4, 5, 6, 6, 7, 8 };
var x = list.GroupBy(x=>x).FirstOrDefault(g=>g.Count()>1).Key;//C#3

Posted 27-Nov-14 0:39am

Neetin_1809

Updated 27-Nov-14 1:17am

v2

Solution 4

Hi
Thank you for quickly solution

Posted 26-Nov-14 23:07pm

smoula99

Comments

Afzaal Ahmad Zeeshan 27-Nov-14 5:28am

You should always post things like this as comments to the post and not as answers. :-)

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Marcin Kozub · Accepted Answer · 2014-11-26T22:55:00

Solution 2

Hello,

C#

var input = new List<int>() { 1, 2, 5, 2, 8, 7, 8, 2 };
var output = (from x in input
                where input.Count(c => c == x) > 1
                select x).ToList();

Console.WriteLine(string.Join(", ", input));
Console.WriteLine(string.Join(", ", output));

I hope it help you.

Posted 26-Nov-14 22:55pm

Marcin Kozub

Updated 26-Nov-14 22:57pm

v3

OriginalGriff · Accepted Answer · 2014-11-26T23:04:00

Since you tagged as LINQ, here is a LINQ method solution:

C#

            List<int> data = "1,2,5,2,8,7,8,2".Split(',').Select(s => int.Parse(s)).ToList();  //Setup input list

            List<int> repeats = data.GroupBy(i => i).Where(g => g.Count() != 1).Select(g => g.Key).ToList(); // So it's done once only.
            List<int> duplicates = data.Where(i => repeats.Contains(i)).ToList();

            foreach (int i in duplicates) Console.WriteLine(i);
</int>

Afzaal Ahmad Zeeshan · Accepted Answer · 2014-11-26T22:53:00

Try this code, it would work for you to get the only elements that are duplicated in the List.

C#

// example list that I tried in my IDE, write your own list here
List<int> list = new List<int>() { 1, 3, 3, 4, 5, 6, 6, 7, 8 };
// run the loop
foreach (int i in list.GroupBy(s => s)
                  .SelectMany(grp => grp.Skip(1)))
{
   // print each element, you can do any other task on it too
   Console.WriteLine(i);
}

.. this will provide you with the only elements that are distinct. In the above context 3 and 6 were printed on screen.