此异步方法缺少“等待”运算符，将同步运行

Question

my program has 3 warnings of the following statement:

This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

What is the warning try to tell me? What should I do?

This is my code: Is it running using multi-threading?

static void Main(string[] args)
{
    Task task1 = new Task(Work1);
    Task task2 = new Task(Work2);
    Task task3 = new Task(Work3);

    task1.Start();
    task2.Start();
    task3.Start();

    Console.ReadKey();
}

static async void Work1()
{
    Console.WriteLine("10 started");
    Thread.Sleep(10000);
    Console.WriteLine("10 completed");
}

static async void Work2()
{
    Console.WriteLine("3 started");
    Thread.Sleep(3000);
    Console.WriteLine("3 completed");
}

static async void Work3()
{
    Console.WriteLine("5 started");
    Thread.Sleep(5000);
    Console.WriteLine("5 completed");
}

Answer 1

The async keyword, by itself, doesn't really do much. Remove it from your code and your code will act exactly the same.

What does async do?

• It changes what's valid inside of the method, specifically it allows you to use the await keyword
• In turn, it means that the body of the method will be transformed, based on the await s that are present in the body of the method.
• And if the method returns a value, the method is also transformed to wrap the return value in a Task .

However, if you a) Don't have any await s in your method body and b) are void returning, then nothing special will be achieved. The compiler warning does try to be clear about this - an async method without any await s just plain doesn't make sense. await s are the more important part of this feature.

Answer 2

if you are overriding and async method with a sync method you can :

await Task.Run(() => [YOUR SYNC METHOD]);

Answer 3

Yes, your code will probably use multi-threading. However, it would still do so if you just removed the async keyword. As you did not explain why it's there, I suggest removing it.

If you want an async/await pattern, you can use Task.Delay() but I would suggest you read more on async/await before using it:

static async void Work3()
{
    Console.WriteLine("5 started");
    await Task.Delay(5000);
    Console.WriteLine("5 completed");
}

Answer 4

You have used ' async ' keyword with method which indicates that Work1(),Work2() and Work3() methods are executed asynchronously,but you have not used 'await' keyword.So it executed as synchronously.Use ' await ' keyword if you want to execute it asynchronously.

 static async void Work1()
 {
     Console.WriteLine("10 started");
     await Task.Delay(10000);
     Console.WriteLine("10 completed");
 }

 static async void Work2()
 {
     Console.WriteLine("3 started");
     await Task.Delay(3000);
     Console.WriteLine("3 completed");
 }

 static async void Work3()
 {
     Console.WriteLine("5 started");
     await Task.Delay(5000);
     Console.WriteLine("5 completed");
 }

Answer 5

您使用关键字async指定了方法（Work1、Work2、Work3），但这些方法中的任何代码都没有使用await运算符来调用异步调用。