C# async and await

async and await let a program wait for slow work (a web request, a file) without freezing. A method marked async returns a Task. Here two tasks run, and their results are collected in a fixed order so the output is predictable.

ExampleC#

using System;
using System.Threading.Tasks;

class Program
{
    static async Task<int> SlowSquareAsync(int n)
    {
        await Task.Delay(50);
        return n * n;
    }

    static async Task Main()
    {
        Task<int> a = SlowSquareAsync(3);
        Task<int> b = SlowSquareAsync(4);
        int[] results = await Task.WhenAll(a, b);
        Console.WriteLine(results[0] + " " + results[1]);

        int single = await SlowSquareAsync(5);
        Console.WriteLine(single);
    }
}

Output

9 16
25

Quick check

What does await do?

Waits for a task without blocking the threadStarts a new programEnds the method

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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