1static class Program
 2    {
 3        static string path = @"c:\file.txt";//确保你本地有这个文件
 4        const int bufferSize = 5;//演示,一次只读取5 byte
 5        static void Main()
 6        {
 7            FileStream fs = new FileStream(path, FileMode.Open,
 8FileAccess.Read, FileShare.Read, 20480, false);//同步调用false
 9            using (fs)//使用using来释放FileStream资源
10            {
11                byte[] data = new byte[bufferSize];
12                StringBuilder sb = new StringBuilder(500);
13                int byteReads;
14                do// 不断循环,直到读取完毕
15                {
16                    byteReads = fs.Read(data, 0, data.Length);
17                    sb.Append(Encoding.ASCII.GetString(data, 0, byteReads));
18                } while (byteReads > 0);
19                Console.WriteLine(sb.ToString());//输出到工作台
20
21            }//自动清除对象资源,隐式调用fs.Close();
22            Console.ReadLine();// 让黑屏等待,不会直接关闭..
23        }
24    }

1static class Program
 2    {
 3        static string path = @"c:\file.txt";//确保你本地有这个文件
 4        const int bufferSize = 5;//演示,一次只读取5 byte
 5        static byte[] data;
 6        static void Main()
 7        {
 8            data = new byte[bufferSize];
 9            FileStream fs = new FileStream(path, FileMode.Open,
10FileAccess.Read, FileShare.Read, 20480, true);//设置异步调用true, 注意0
11
12            //异步读取文件,把FileStream对象作为异步的参数// <-
13            AsyncCallback callback = new AsyncCallback(OnReadCompletion);
14            IAsyncResult async = fs.BeginRead(data, 0, bufferSize, callback, fs); // <-
15
16            Console.ReadLine();// 让黑屏等待,不会直接关闭..
17        }
18        static void OnReadCompletion(IAsyncResult asyncResult)
19        {
20            FileStream fs = asyncResult.AsyncState as FileStream;
21            int bytesRead = fs.EndRead(asyncResult);
22            //输出到工作台
23            Console.Write(Encoding.ASCII.GetString(data, 0, bytesRead));
24            //不断循环,直到读取完毕
25            if (bytesRead > 0)
26                fs.BeginRead(data, 0, bufferSize, OnReadCompletion, fs);
27            else
28                fs.Close(); //当全部读取完毕,显式释放资源
29        }
30    }

1static class Program
 2    {
 3        static string path = @"c:\file.txt";//确保你本地有这个文件
 4        const int bufferSize = 5;//演示,一次只读取5 byte
 5        static void Main()
 6        {
 7            byte[] data = new byte[bufferSize];
 8            //[1]
 9            FileStream fs = new FileStream(path, FileMode.Open,
10FileAccess.Read, FileShare.Read, 20480, true);//设置异步调用true
11            //使用匿名委托方式
12            AsyncCallback callback = null; //注意1
13            callback = delegate(IAsyncResult asyncResult)//匿名方法
14            {
15                int bytesRead = fs.EndRead(asyncResult);//[2]
16                Console.Write(Encoding.ASCII.GetString(data, 0, bytesRead));//输出到工作台
17                //不断循环,直到读取完毕
18                if (bytesRead > 0)
19                    fs.BeginRead(data, 0, bufferSize, callback, null);//[3]
20                else
21                    fs.Close();//[4]
22            };
23
24            //异步读取文件
25            IAsyncResult async = fs.BeginRead(data, 0, bufferSize, callback, null);
26
27            Console.ReadLine();// 让黑屏等待,不会直接关闭..
28        }
29    }

static class Program
    {
        static string path = @"c:\file.txt";//确保你本地有这个文件
        const int bufferSize = 5;//演示,一次只读取5 byte
        static void Main()
        {
            byte[] data = new byte[bufferSize];

FileStream fs = new FileStream(path, FileMode.Open,
FileAccess.Read, FileShare.Read, 20480, true);//设置异步调用true
            //使用lambda 表达式
            AsyncCallback callback = null;//注意1
            callback = asyncResult =>
            {
                int bytesRead = fs.EndRead(asyncResult);
                Console.Write(Encoding.ASCII.GetString(data, 0, bytesRead));//输出到工作台
                //不断循环,直到读取完毕
                if (bytesRead > 0)
                    fs.BeginRead(data, 0, bufferSize, callback, null);
                else
                    fs.Close();
            };

//异步读取文件
            IAsyncResult async = fs.BeginRead(data, 0, bufferSize, callback, null);

Console.ReadLine();// 让黑屏等待,不会直接关闭..
        }
    }

1static class Program
 2    {
 3        static void Main()
 4        {
 5            FileStream fs = new FileStream("text.txt", FileMode.Create,
 6FileAccess.ReadWrite, FileShare.None, 20480, true);//设置异步调用true
 7            //输入信息
 8            Console.Write("Please Enter:");
 9            byte[] data = Encoding.ASCII.GetBytes(Console.ReadLine());
10
11            //异步写文件
12            IAsyncResult async = fs.BeginWrite(data, 0, data.Length, asyncResult =>
13            {
14                fs.EndWrite(asyncResult);//写文件介绍,输出到text.txt文件中.
15                fs.Close();
16
17            }, null);
18
19            Console.ReadLine();// 让黑屏等待,不会直接关闭..
20        }
21    }