1. What is this?
A loop repeats a block. A list (List<string>) holds many values in order. APIs often return lists as JSON: ["Ava","Liam"]. foreach walks a list one item at a time without an index.
2. Why do we use it?
Feeds, search results, and catalogues are lists served over HTTP.
3. Syntax breakdown
var names = new List<string> { "Ava", "Liam" };Creates a list of two strings. var infers the type.
foreach (var n in names) {Repeats once per item, calling it n each time.
Console.WriteLine(n); }
Prints each item on its own line.
5. Common mistakes
- Forgetting using System.Collections.Generic; for List<T>.
- Modifying a list while foreach walks it — collect changes and apply after.
- Returning internal mutable lists directly from an API (copy or project first).
Practice task
Add "Noah" to the list and print all four names.
Hint
Add, "Noah" inside the { ... } initializer.
Try it below — tests run automatically when you press Run.
dotnet
Output
Press Run to see output.
Mini quiz
3 questions. Answer, then check.
1. What is a List<string>?
2. What does foreach do?
3. What do APIs often return for collections?