Concat of two list using LINQ

Question

I have two list list1 and list2

List1 contains

1   a
2   b
3   c
4   d

List2 contains

3   c
4   d
5   e

I want following list using LINQ

1   a
2   b
3   c
4   d
5   e

Answer 1

List1.Concat(List2.Where(l2 => !List1.Contains(l2))).ToList()

Answer 2

Since I don't see this answer here i'll post it...

The best way to remove duplicates while merging two lists together is Enumerable.Union:

var foo = new List<char> { 'a', 'b', 'c', 'd' };
var bar = new List<char> { 'c', 'd', 'e' };

var result = foo.Union(bar).ToList();

The rest of the answers work, but Linq has a built-in way to do this.

Answer 3

var Lst = List1.Concat(List2.Where(l2 => List1.All(x => x.Id != l2.Id))).ToList();