What is this syntax for initializing collections called?

I have a basic C# program to demonstrate this:

namespace ConsoleApp5
{
    internal class Program
    {
        static void Main(string[] args)
        {
            List<int> list = [1, 2, 3, 4, 5, 6];
            List<int> list2 = [.. list];
        }
    }
}

What is the name for the trick being used to initialize list2?

>Solution :

They’re known as collection expressions, introduced in C# 12 / .NET 8:

A collection expression is a terse syntax that, when evaluated, can be assigned to many different collection types. A collection expression contains a sequence of elements between [ and ] brackets

The [.. list] syntax is known as a spread element, it’s the same as inlining the entire list:

You use a spread element .. to inline collection values in a collection expression.