This code inspection checks that trailing commas in single-line declarations with multiple items and similar constructs (object, array, and collection initializers, as well as enums and switch expressions) conform to your code style.
Depending on your preferences, it either detects redundant trailing commas or missing trailing commas.
The preferences are configured on the Editor | Code Style | C# | Syntax Style page of JetBrains Rider settings , under Trailing comma.