C# async await的使用

async 聲明一個包含異步代碼的函數，該函數執行時不會阻塞調用線程。

async標記的函數返回值必須為 void ,Task,Task<TResult>

await 必須修飾Task 或者Task<TResult>

await之后的代碼運行線程：對於純console工程，還是耗時任務的線程，

對於winform線程，則是調用線程。

 

典型代碼

 

        public static async Task<int> CalAsync()
        {
            string tid = Thread.CurrentThread.ManagedThreadId.ToString();
            Console.WriteLine("當前位置async函數，await之前，線程ID"+tid);
            int result = await Task.Run(new Func<int>(Cal));
            tid = Thread.CurrentThread.ManagedThreadId.ToString();
            Console.WriteLine("當前位置async函數，await之后，線程ID" + tid);
            return result;
        }

全部代碼

class Program
    {
        static void Main(string[] args)
        {
            string tid = Thread.CurrentThread.ManagedThreadId.ToString();
            Console.WriteLine("當前位置主函數，調用async異步之前，線程ID"+tid);
            Task<int> t = CalAsync();
            Console.WriteLine("當前位置主函數，調用async異步之后，線程ID" + tid);
            Console.Read();

        }
        public static async Task<int> CalAsync()
        {
            string tid = Thread.CurrentThread.ManagedThreadId.ToString();
            Console.WriteLine("當前位置async函數，await之前，線程ID"+tid);
            int result = await Task.Run(new Func<int>(Cal));
            tid = Thread.CurrentThread.ManagedThreadId.ToString();
            Console.WriteLine("當前位置async函數，await之后，線程ID" + tid);
            return result;
        }

        public static int Cal()
        {
            string tid = Thread.CurrentThread.ManagedThreadId.ToString();
            Console.WriteLine("當前位置耗時函數，線程ID"+tid);
            int sum = 0;
            for (int i = 0; i < 999; i++)
            {
                sum = sum + i;
            }
            Console.WriteLine("當前位置耗時函數完成，線程ID" + tid);
            return sum;
        }


    }

輸入內容

 

 

winform中優雅的實現

private async void button1_Click(object sender, EventArgs e)
        {
            var t = Task.Run(() =>
            {
                Thread.Sleep(5000);
                return "Returning from TimeConsuming task";
            });
            this.Text = await t;
        }

 

 

參考

https://www.cnblogs.com/doforfuture/p/6293926.html