How is the usage of ‘await’ in C#?

In C#, the await keyword is used to wait for an asynchronous operation to complete and allows the program to continue executing other operations while waiting. It can only be used in asynchronous methods and can only be used with methods that return Task or Task types.

When using the await keyword, you need to follow the following steps:

1. Done at a later time
2. wait for
3. Assignment
4. Generic task with type T
5. wait
6. null
7. Job
8. Generic type Task with type parameter T

For example, you can use the ‘await’ keyword to wait for the completion of an asynchronous call.

async Task SomeAsyncMethod()
{
    // 异步调用
    await SomeAsyncOperation(); // 等待异步操作完成

    // 继续执行其他操作
    Console.WriteLine("Async operation completed.");
}

In the example above, await SomeAsyncOperation() signifies waiting for the asynchronous operation of the SomeAsyncOperation() method to complete. Once the asynchronous operation is finished, the program will proceed to execute the statement Console.WriteLine(“Async operation completed.”).

It is important to note that the await keyword can only be used inside asynchronous methods, not in synchronous methods or constructors. Furthermore, if you need to wait for multiple asynchronous operations to complete within an asynchronous method, you can use multiple await expressions to wait for them to complete in order.