下载网络资源-带下载进度

带进度 http://t.zoukankan.com/h82258652-p-10950580.html

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namespace AppUtils {     public struct HttpDownloadProgress     {         public long BytesReceived { get; set; }         public long TotalBytesToReceive { get; set; }     }     public static class HttpClientExtensions     {         private const int BufferSize = 8192;           public static async Task<byte[]> GetByteArrayAsync(this HttpClient client, Uri requestUri, IProgress<HttpDownloadProgress> progress, CancellationToken cancellationToken)         {             if (client == null)             {                 throw new ArgumentNullException(nameof(client));             }               using (var responseMessage = await client.GetAsync(requestUri, HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false))             {                 if (responseMessage.StatusCode== System.Net.HttpStatusCode.NotFound)                 {                     throw new Exception(System.Net.HttpStatusCode.NotFound.ToString());                 }                 responseMessage.EnsureSuccessStatusCode();                   var content = responseMessage.Content;                 if (content == null)                 {                     return Array.Empty<byte>();                 }                   var headers = content.Headers;                 var contentLength = headers.ContentLength;                 using (var responseStream = await content.ReadAsStreamAsync().ConfigureAwait(false))                 {                     var buffer = new byte[BufferSize];                     int bytesRead;                     var bytes = new List<byte>();                       var downloadProgress = new HttpDownloadProgress();                     if (contentLength.HasValue)                     {                         downloadProgress.TotalBytesToReceive = contentLength.Value;                     }                     progress?.Report(downloadProgress);                     while ((bytesRead = await responseStream.ReadAsync(buffer, 0, BufferSize, cancellationToken).ConfigureAwait(false)) > 0)                     {                         bytes.AddRange(buffer.Take(bytesRead));                           downloadProgress.BytesReceived += bytesRead;                         progress?.Report(downloadProgress);                     }                       return bytes.ToArray();                 }             }         }     } }

　　UpgradeService：System.Net.Http.HttpClient _client = new HttpClient();

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public async Task DownloadFileAsync(string url, IProgress<HttpDownloadProgress> progress, CancellationToken token)         {             var filePath = "D:\test.txt";             if (File.Exists(filePath))             {                 File.Delete(filePath);             }               var bytes = await _client.GetByteArrayAsync(new Uri(url), progress, token);             using var fileStream = new FileStream(filePath, FileMode.Create);             fileStream.Write(bytes, 0, bytes.Length);         }

　　

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string fileUrl = "http://xxxxx/test.txt";             CancellationTokenSource CTSource = new CancellationTokenSource();             //当前线程             var progress = new Progress<HttpDownloadProgress>(async percent =>             {                 BytesReceived = percent.BytesReceived / 1024; //当前已经下载的Kb                 TotalBytesToReceive = percent.TotalBytesToReceive / 1024; //文件总大小Kb                 DownloadMsg = "正在下载： " + BytesReceived + "KB / " + TotalBytesToReceive + "KB";                 //StateHasChanged();                   //await moduleJS.InvokeVoidAsync("SetDownloadMsg", DownloadMsg);               });             await _UpgradeService.DownloadFileAsync(fileUrl, progress, CTSource.Token);

旧代码：

#region 下载文件
    /// <summary>
    /// Http方式下载文件
    /// </summary>
    /// <param name="url">http地址</param>
    /// <param name="localfile">本地文件</param>
    /// <returns></returns>
    public bool Download(string url, string localfile)
    {
        bool flag = false;
        long startPosition = 0; // 上次下载的文件起始位置
        FileStream writeStream; // 写入本地文件流对象

        long remoteFileLength = GetHttpLength(url);// 取得远程文件长度
        System.Console.WriteLine("remoteFileLength=" + remoteFileLength);
        if (remoteFileLength == 745)
        {
            System.Console.WriteLine("远程文件不存在.");
            return false;
        }

        // 判断要下载的文件夹是否存在
        if (File.Exists(localfile))
        {

            writeStream = File.OpenWrite(localfile);             // 存在则打开要下载的文件
            startPosition = writeStream.Length;                  // 获取已经下载的长度

            if (startPosition >= remoteFileLength)
            {
                System.Console.WriteLine("本地文件长度" + startPosition + "已经大于等于远程文件长度" + remoteFileLength);
                writeStream.Close();

                return false;
            }
            else
            {
                writeStream.Seek(startPosition, SeekOrigin.Current); // 本地文件写入位置定位
            }
        }
        else
        {
            writeStream = new FileStream(localfile, FileMode.Create);// 文件不保存创建一个文件
            startPosition = 0;
        }


        try
        {
            HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(url);// 打开网络连接

            if (startPosition > 0)
            {
                myRequest.AddRange((int)startPosition);// 设置Range值,与上面的writeStream.Seek用意相同,是为了定义远程文件读取位置
            }


            Stream readStream = myRequest.GetResponse().GetResponseStream();// 向服务器请求,获得服务器的回应数据流


            byte[] btArray = new byte[512];// 定义一个字节数据,用来向readStream读取内容和向writeStream写入内容
            int contentSize = readStream.Read(btArray, 0, btArray.Length);// 向远程文件读第一次

            long currPostion = startPosition;

            while (contentSize > 0)// 如果读取长度大于零则继续读
            {
                currPostion += contentSize;
                int percent = (int)(currPostion * 100 / remoteFileLength);
                System.Console.WriteLine("percent=" + percent + "%");

                writeStream.Write(btArray, 0, contentSize);// 写入本地文件
                contentSize = readStream.Read(btArray, 0, btArray.Length);// 继续向远程文件读取
            }

            //关闭流
            writeStream.Close();
            readStream.Close();

            flag = true;        //返回true下载成功
        }
        catch (Exception)
        {
            writeStream.Close();
            flag = false;       //返回false下载失败
        }

        return flag;
    }

    // 从文件头得到远程文件的长度
    private static long GetHttpLength(string url)
    {
        long length = 0;

        try
        {
            HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);// 打开网络连接
            HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();

            if (rsp.StatusCode == HttpStatusCode.OK)
            {
                length = rsp.ContentLength;// 从文件头得到远程文件的长度
            }

            rsp.Close();
            return length;
        }
        catch (Exception e)
        {
            return length;
        }

    }
    #endregion