Linq Merge 2 Lists to One

Question

I have two list for example: 1:

 ID | Number
-------------
 01 |   20
 02 |   50
 04 |  2500

2:

 ID | Number
-------------
 01 |   10
 02 |   20
 03 |  1500

And the final list that I want to get back is:

 ID | Number
-------------
 01 |   30
 02 |   70
 03 |  1500
 04 |  2500

How I can done it with Linq?

http://stackoverflow.com/questions/4872943/how-to-merge-two-lists-using-linq — ssilas777, Apr 06 '13 at 11:25

Hossein Narimani Rad · Answer 1 · 2013-04-06T11:33:29.943

6

You can use the Zip method.

public class MyClass
{
    public int Id { get; set; }
    public string Number { get; set; }
}

Then try this:

List<MyClass> fist = new List<MyClass>();     //add some data
List<MyClass> second = new List<MyClass>();   //add some data

fist.Zip(second,
          (i1, i2) => new MyClass() { Id = i1.Id, Number = i1.Number + i2.Number });

edited Apr 06 '13 at 11:33

answered Apr 06 '13 at 11:25

Hossein Narimani Rad

31,361
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score 2 · Accepted Answer · answered Apr 06 '13 at 11:43

I found the answer,

var mergedList = list1.Concat(list2)
                  .GroupBy(person => person.ID)
                  .Select(group => group.Aggregate(
                                     (merged, next) => merged.Merge(next)))
                  .ToList();

Thanks for helping me get the answer.

score 0 · Answer 3 · answered Apr 06 '13 at 11:26

0

You should join the lists. Here is an example:

public class Item
{
    public int ID { get; set; }
    public int Number { get; set; }
}

List<Item> firstList = new List<Item>();
List<Item> secondList = new List<Item>();

List<Item> finalList = firstList.Join(
    secondList,
    item => item.ID,
    item => item.ID,
    (item, item1) => new Item() { ID = item.ID, Number = item.Number + item1.Number }).ToList();

answered Apr 06 '13 at 11:26

Nikolay Kostov

16,433
23
85
123

The Zip method above seems to be 2 times faster than joining lists. – Nikolay Kostov Apr 06 '13 at 11:40

Linq Merge 2 Lists to One

3 Answers3