异步方法读取网络路径异步读取文件字符流

最新推荐文章于 2022-10-08 17:29:32 发布

mlovelcottage

最新推荐文章于 2022-10-08 17:29:32 发布

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分类专栏： c#后台文章标签：异步读取地址事件event 异步读取文件

本文链接：https://blog.youkuaiyun.com/miluli1/article/details/85993940

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本文详细介绍了异步读取网络地址信息及文件字符流的方法，包括异步请求网络资源、处理响应流，以及异步读取本地文件并使用事件驱动模型进行数据处理的完整过程。

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1.异步读取地址下信息

        public void T_Invoke()
        {
            var request = WebRequest.Create("http://www.sina.com.cn");
            //io  yibu
            request.BeginGetRequestStream(AsyncCallbackImpl, request);
        }
        public void AsyncCallbackImpl(IAsyncResult ar)
        {
            WebRequest request = ar.AsyncState as WebRequest;
            var reponse = request.EndGetResponse(ar);
            var stream = request.GetRequestStream();
            using (StreamReader reader=new StreamReader(stream))
            {
                //values
                string str=reader.ReadLine();
            }
        }

2.异步时间读取路径下文件字符流信息

        public event EventHandler<ReturnEndReadEventargs> IsReturnEvent;

        FileStream InputStream;
        StringBuilder ReadValue;
        byte[] buffer;
        public string ReadFileAsync(string fileName)
        {
            ReadValue = new StringBuilder();
            int BufferSize=0;
            buffer = new byte[BufferSize];

            InputStream = new FileStream(fileName, FileMode.Open, FileAccess.Read,
                FileShare.Read, BufferSize, useAsync: true);
            InputStream.BeginRead(buffer, 0, buffer.Length, OnCompleteRead, null);
            //InputStream.write
            return ReadValue.ToString();
        }

        public void OnCompleteRead(IAsyncResult asyncResult)
        {
            //异步读取一个快，接收数据
            int bytesRead = InputStream.EndRead(asyncResult);
            //如果没有任何字节，则流已达文件结尾
            if (bytesRead > 0)
            {
                //暂停以对模拟对数据块的处理
                Debug.WriteLine("异步线程：已读取一块内容");
                var datastr = Encoding.UTF8.GetString(buffer, 0, buffer.Length);
                ReadValue.Append(datastr);
                Thread.Sleep(TimeSpan.FromMilliseconds(20));
                //开始读取下一块
                InputStream.BeginRead(buffer, 0, buffer.Length, OnCompleteRead, null);
            }
            else
            {
                //操作结束
                Debug.WriteLine("   异步线程：读取文件结束");
                //event必须方法里调用
                OnIsReturnEvent();
            }
        }
        protected virtual void OnIsReturnEvent()
        {
            IsReturnEvent?.Invoke(this, new ReturnEndReadEventargs(true, ReadValue.ToString()));
            //IsReturnEvent(this, new ReturnEndReadEventargs(true, ReadValue.ToString()));
        }
        public class ReturnEndReadEventargs : EventArgs
        {
            public ReturnEndReadEventargs(bool isReturn, string value)
            {
                IsReturn = isReturn;
                ReadValue = value;
            }
            public string ReadValue { get; set; }
            public bool IsReturn { get; set; }
        }