is it possible to initialize a List with other List's in C#? Say I've got these to lists:

```
List<int> set1 = new List<int>() {1, 2, 3};
List<int> set2 = new List<int>() {4, 5, 6};

```

What I'd like to have is a shorthand for this code:

```
List<int> fullSet = new List<int>();
fullSet.AddRange(set1);
fullSet.AddRange(set2);

```

Thanks in advance!
['https://Stackoverflow.com/questions/1404832', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/16440/']
To allow duplicate elements (as in your example):

```
List<int> fullSet = set1.Concat(set2).ToList();

```

This can be generalized for more lists, i.e. `...Concat(set3).Concat(set4)`. If you want to remove duplicate elements (those items that appear in both lists):

```
List<int> fullSet = set1.Union(set2).ToList();

```
```
List<int> fullSet = new List<int>(set1.Union(set2));

```

may work.