How can I concatenate two C# Lists of the type List<KeyValuePair<string,string>>. I have some duplicate values and I need those duplicate values

Thursday, August 2, 2012 by Nate Bross

Someone asked on Stack Overflow:

Any LINQ solutions (preferably) would be appreciated. I need the duplicate values upon concatenating both.

I posted the following answer, which was chosen as the accepted answer and received 1 upvote:

If you want to find out which items are in both lists, you need to use the Enumerable.Intersect() method.

    var list1 = new List<KeyValuePair<string,string>>();
    var list2 = new List<KeyValuePair<string,string>>();

    list1.Add(new KeyValuePair<string,string>("key1", "value1"));
    list1.Add(new KeyValuePair<string,string>("key2", "value2"));
    list2.Add(new KeyValuePair<string,string>("key1", "value1"));
    list2.Add(new KeyValuePair<string,string>("key3", "value3"));

    var inBothLists = list1.Intersect(list2); // contains only key1,value1

There are two overloads, one takes an IEqualityComparer<T> so in the event that the default one does not perform the comparison the way you want, you can write and provide your own.

Originally posted on Stack Overflow — 1 upvotes (accepted answer). Licensed under CC BY-SA.