C# 中的Async 和 Await 方法的实际应用

 

注意 Method 3需要一个参数，即Method 1的返回类型。在这里，await关键字对于等待Method 1任务的完成起着至关重要的作用。

 

 

static void Main(string[] args)
        {
            Console.OutputEncoding = Encoding.UTF8;
            callMethod();
            Console.WriteLine("callMethod");
            Console.ReadKey();
        }

        public static async  void callMethod()
        {
            Task<int> task = Method1();
            Method2();
            int count = await task; // 后面的代码阻塞，直到 Method1  执行完

            Method3(count);
        }

        public static async Task<int> Method1()
        {
            int count = 0;
          var t=   Task.Run(() =>   // 开始异步
            {
                for (int i = 0; i < 25; i++)
                {
                    Thread.Sleep(10);
                    Console.WriteLine(" Method 1");
                    count += 1;
                }
            });
            await t;  // 主线程继续,没有 await ，主线程会继续阻塞

            return count;
        }

        public static async void Method2()
        {
            await Task.Run(()=> {
                for (int i = 0; i < 25; i++)
                {
                    Thread.Sleep(10);
                    Console.WriteLine(" Method 2");
                }
            }); 
        }

        public static void Method3(int count)
        {
            Console.WriteLine("Total count is " + count);
        }

　　

在扫描一段文本内容之后，需要执行一段逻辑。最后等待读取的内容长度。这里就实际应用了异步的思想

 

 

 

class Program
{  
    static void Main()
    {  
Task task = new Task(CallMethod);
task.Start();
task.Wait();
Console.ReadLine();
    }  
  
    static async void CallMethod()
    {  
        string filePath = "E:\\sampleFile.txt";  
Task<int> task = ReadFile(filePath);
  
Console.WriteLine(" Other Work 1");  
Console.WriteLine(" Other Work 2");  
Console.WriteLine(" Other Work 3");  
  
        int length = await task;
Console.WriteLine(" Total length: " + length);
  
Console.WriteLine(" After work 1");  
Console.WriteLine(" After work 2");  
    }  
  
    static async Task<int> ReadFile(string file)
    {  
        int length = 0;
  
Console.WriteLine(" File reading is stating");  
        using (StreamReader reader = new StreamReader(file))
        {  
            // Reads all characters from the current position to the end of the stream asynchronously   
            // and returns them as one string.   
            string s = await reader.ReadToEndAsync();
  
length = s.Length;
        }  
Console.WriteLine(" File reading is completed");  
        return length;
    }  
}