Combine two list<> and remove the duplicates in it

Question

I have two list objects. I combine them to a single list. Whilst combining I need to remove the duplicates. TweetID is the field to be compared.

List<TweetEntity> tweetEntity1 = tt.GetTweetEntity(Convert.ToInt16(pno), qdecoded, longwoeid );
List<TweetEntity> tweetEntity2 = tt.GetTweetEntity(Convert.ToInt16(pno), qdecoded);
List<TweetEntity> tweetEntity = tweetEntity1.Concat(tweetEntity2).ToList();

I have combined the two lists but unable to filter out the duplicates. Is there any inbuilt function to remove the duplicates in List<>?

Have you tried searching for an answer? http://stackoverflow.com/questions/4031262/how-to-merge-2-listt-with-removing-duplicate-values-in-c-sharp http://stackoverflow.com/questions/3682437/combining-2-lists-and-and-remove-duplicates-output-in-a-third-list-my-attempts — SpaceSteak, Sep 03 '15 at 14:42
This is not duplicate as here the list item is itself a complex object. The answers in the link are simple list of integer objects. — Venkat, Sep 03 '15 at 15:07
Same idea, except you have to consider searching for properties instead of just the value. You're allowed to extrapolate more complexity from a question. — SpaceSteak, Sep 03 '15 at 15:09

score 6 · Answer 1 · answered Sep 03 '15 at 14:44

6

You could make use of Union method.

List<TweetEntity> tweetEntity = tweetEntity1.Union(tweetEntity2).ToList();

However, you have at first override Equals and GetHashCode for TweetEntity.

answered Sep 03 '15 at 14:44

Christos

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Or pass an `IEqualityComparer`, since equality may already have been implemented. – Caramiriel Sep 03 '15 at 14:47

score 1 · Answer 2 · answered Sep 03 '15 at 14:43

1

You can use Distinct() method.

tweetEntity1.Concat(tweetEntity2).Distinct().ToList();

answered Sep 03 '15 at 14:43

Andrey Korneyev

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Using `Union` is the better approach, because this method already filters out duplicates. – Ramon de Klein Sep 03 '15 at 14:46

score 1 · Answer 3 · answered Sep 03 '15 at 14:44

1

use the Union linq extension,

tweetEntity1.Union(tweenEntity2).ToList()

functionally equivalent to .Concat and Distinct combined but easier to type and faster to run,

answered Sep 03 '15 at 14:44

Jodrell

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score 0 · Answer 4 · answered Sep 03 '15 at 14:46

0

You can use the linq Distinct method, however you'll have to implement IEqualityComparer<T>.

public class TweetEntityComparer<TweetEntity> 
{
    public bool Equals(TweetEntity x, TweetEntity y)
    {
        //Determine if they're equal
    }

    public int GetHashCode(TweetEntity obj)
    {
        //Implementation
    }
}

List<TweetEntity> tweetEntity = tweetEntity1.Concat(tweetEntity2).Distinct().ToList();

You could also alternatively use Union.

List<TweetEntity> tweetEntity = tweetEntity1.Union(tweetEntity2).ToList();

answered Sep 03 '15 at 14:46

Dave Zych

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Union doesnot work. Since my list object is a class. – Venkat Sep 03 '15 at 15:02
I donot know how to implement this IEqualityComparer. Can you please elaborate. – Venkat Sep 03 '15 at 15:06

Combine two list<> and remove the duplicates in it

4 Answers4