How compare two List<T>?

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I have class

C#

public class DB
{
    public string answer{ get; set; }
    public string question { get; set; }
    public string url { get; set; }
}

XML

List<DB> list1 = new List<DB>();
List<DB> list2 = new List<DB>();

How get all list elements, where DB.answer is not similar?

Posted 11-Nov-15 23:19pm

Member 11266633

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3 solutions

Solution 3

Write a simple Comparer. Then use Union and pass in the comparer

C#

public   class DBComparer : IEqualityComparer<DB>
    {

        public bool Equals(DB x, DB y)
        {
            return x.answer == y.answer;
        }

        public int GetHashCode(DB db)
        {
            return db.answer.GetHashCode();
        }
    }

   var filteredList = list1.Union(list2,new DBComparer()).ToList();

Posted 12-Nov-15 21:25pm

George Swan

Solution 2

var result = list1.Where(a => list2.Any(b => a.answer != b.answer)).ToList();

-KR

Posted 11-Nov-15 23:50pm

Krunal Rohit

Comments

George Swan 12-Nov-15 15:29pm

Are you sure this is correct? I would have thought that it returns the whole of List1

BillWoodruff 12-Nov-15 15:37pm

Any: "This method does not return any one element of a collection. Instead, it determines whether any elements of a collection satisfy a condition.

The enumeration of source is stopped as soon as the result can be determined."

Did you test this code ?

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Abhinav S · Accepted Answer · 2015-11-11T23:33:00

Solution 1

Try something like list1.Except(list2.select(x=>x.answer)).Union(list2.Except(list1.select(x=>x.answer)).

Basically this is based on the princple, a.Except(b).Union(b.Except(a) which suggests getting all items from lista not in listb and then all in listb not in lista and then putting a union on them.

Posted 11-Nov-15 23:33pm

Abhinav S

Comments

CPallini 12-Nov-15 5:34am

5.

Abhinav S 12-Nov-15 5:44am

Thank you

Member 11266633 12-Nov-15 5:43am

this code not work

Abhinav S 12-Nov-15 5:47am

What did you try?

phil.o 12-Nov-15 7:01am

'not working' is not a valid issue description

BillWoodruff 12-Nov-15 15:10pm

+3 I know you are on the right track here, but note that your code will not compile:

1. Select not select

2. Throws an error: arguments to Except

The moment this code compiles and works, you get my #5 :)

Abhinav S 12-Nov-15 23:55pm

I will leave compilation to the poster... :)