Enumerable.Concat more than two parameters c#

Question

I have 4 collections containing strings, like this:

first: xxxxxxxx second: xx third: xxxxxxxx fourth: xx

I want to concat these 4 collections to get: xxxxxxxxxxxxxxxxxxxx

I wanted to use the Enumerable.Concat but I have one problem with this, It only take two parameters. As a consequence I can concat only the first with the second (for example) but not all of'em together.

Is c# offers a way to concat more than 2 collections together?

Am I having to create two collections which concat first + second and third + fourth and then concat the two collections together?

EDIT

I made a mistake, It's 4 collections I want to concat. These collections contains strings like shown before, but these are Collections

Answer 1

You can chain the Enumerable.Concat calls like this.

List<string> list1 = new List<string>();
List<string> list2 = new List<string>();
List<string> list3 = new List<string>();
List<string> list4 = new List<string>();

//Populate the lists

var mergedList = list1.Concat(list2)
    .Concat(list3)
    .Concat(list4)
    .ToList();

Another option is to create an array and call SelectMany

var mergedList = new[]
{
    list1, list2, list3, list4
}
.SelectMany(x => x)
.ToList();

Note: Enumerable.Concat will allow duplicate elements, if you want to eliminate duplicates you can use Enumerable.Union method, rest all same.