How can I check for identical items and update a list?

Question

I have an amount of items in a list or list_1 . Each item is a row from a database. An import of these items is going to happen on another list, or list_2 . list_2 already contains content of the same type.
Is there a way to make this happen so that only those items that are not present in list_2 get imported?

Note that the original order must be retained in list_2 and the new items are to be imported on top of that original order. The order is important because list_2 actually is a concurrentqueue. So, the content of list_1 should be updated somehow (clearing the duplicates) before I can start importing it into list_2 . The actual import into list_2 (queue) is not a problem, it's the way to clean up list_1 that interests me. Thanks.

Answer 1

using System.Linq;
//...

var strippedList1 = list_1.Except(list_2);

To make this work, you need to make sure that your objects implement Equals / GetHashcode

Answer 2

please look at my below code it may help you

        List<string> l = new List<string>();
        l.Add("1");
        l.Add("2");
        List<string> l1 = new List<string>();
        l1.Add("1");
        var abc = l.Except(l1);