C# 12: Collection literals

[giscus[bot]]

C# 12: Collection literals

A new feature is hitting C# 12 and it is called Collection literals. In this blog post, I will show you what it is and how it works.

https://steven-giesel.com/blogPost/9916410c-0428-4caf-b88e-9fbae72b6a1f

[dimohy]

var items = [1, 2, 3];

Future C# developer candidates will want the clean code above. Is this really possible, or has C# already come a long way?

[linkdotnet]

The propsal intends the usage you describe above. Depending hin the context it should choose the „best“ option possible.

[KennethHoff]

Generally speaking, List is the "standard collection" in C#, so var items = [1, 2, 3]; would be equal to List<int> items = [1, 2, 3]; which itself would be more-or-less the same as List<int> items = new List<int>() {1, 2, 3};.
IIRC there are differences between the new way(= [1,2,3]) and the old way( =new List<....) in terms of how it works though - the new one is more performant I believe

[linkdotnet]

In its current stage, it does get lowered to somewhat the same code. But the proposal goes a bit further. Just imagine this:

private void MyFunc()
{
  var a = [1, 2, 3];
  // Do something with a
}

a could be either of type Span<int> or just int[] as this is more performant. I do like this though.

[KennethHoff]

I realize now that my comment was very affirmative - pretending like I know what I'm talking about - but after posting it I did some more reading up on the WG drafts and it does seem like there is no defined natural type for this. The only definite thing was that var a = [] will not be allowed in the first version.

It would be really cool if they used Spans in scenarios where they've concluded that it could - Free performance!