async and await

Context: The async and await keywords are the core of asynchronous programming in C#. They allow you to write non‑blocking code that looks like synchronous code.

How it works

• async marks a method as asynchronous, allowing the use of await.
• await suspends the method until the awaited task completes, without blocking the thread.

public async Task ProcessDataAsync()
{
    Console.WriteLine("Start");
    await Task.Delay(1000); // non‑blocking wait
    Console.WriteLine("After delay");
}

Real-world usage example

Web API controllers: Mark actions as async and await database calls, HTTP calls, or file I/O.

Example: ASP.NET Core async actions improve scalability.

Related sections

• 9.2.1 Marking method async
• 9.2.2 await unwraps the result
• 9.2.3 Compiler transformation into state machine