# C# 15: Collection expression arguments

Collection expression arguments on one page: with(...) passes a comparer or a capacity into the square brackets. From the blog post \[What's new in C# 15: Collection expression arguments\](/blog/whats-new-in-csharp-15-collection-expression-arguments).

![The cheat sheet C# 15: Collection expression arguments, with Codey: the three points of the post on one page](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/dc4a32334aed4f9bbd8a9fffe2cedc19.webp)

- Category: C#
- Level: Apprentice
- Tags: csharp, csharp-15, whats-new
- Updated: November 11, 2026

Source: https://www.ask-codey.com/cheat-sheets/csharp-15-collection-expression-arguments-cheat-sheet