c# - 如何以及何时使用“异步”和“等待”(How and when to use ‘async’ and ‘await’)

Question

From my understanding one of the main things that async and await do is to make code easy to write and read - but is using them equal to spawning background threads to perform long duration logic?

(根据我的理解， async和await要做的主要事情之一就是使代码易于编写和读取-但是使用它们是否等于生成后台线程来执行长时间逻辑？)

I'm currently trying out the most basic example.

(我目前正在尝试最基本的示例。)

I've added some comments inline.

(我在行中添加了一些评论。)

Can you clarify it for me?

(你能为我澄清一下吗？)

// I don't understand why this method must be marked as `async`.
private async void button1_Click(object sender, EventArgs e)
{
    Task<int> access = DoSomethingAsync();
    // task independent stuff here

    // this line is reached after the 5 seconds sleep from 
    // DoSomethingAsync() method. Shouldn't it be reached immediately? 
    int a = 1; 

    // from my understanding the waiting should be done here.
    int x = await access; 
}

async Task<int> DoSomethingAsync()
{
    // is this executed on a background thread?
    System.Threading.Thread.Sleep(5000);
    return 1;
}

  ask by Dan Dinu translate from so