Winform中文件的下载

1、直接下载

using (HttpClient http = new HttpClient())
{
    var httpResponseMessage = await http.GetAsync("http://localhost:813/新建文件夹2.rar", HttpCompletionOption.ResponseHeadersRead);//发送请求
    var contentLength = httpResponseMessage.Content.Headers.ContentLength;//读取文件大小

    using (var stream = await httpResponseMessage.Content.ReadAsStreamAsync())//读取文件流
    {
        var readLength = 1024000;//1000K  每次读取大小
        byte[] bytes = new byte[readLength];
        int writeLength;
        while ((writeLength = stream.Read(bytes, 0, readLength)) > 0)//分块读取文件流
        {
            using (FileStream fs = new FileStream(Application.StartupPath + "/temp.rar", FileMode.Append, FileAccess.Write))//使用追加方式打开一个文件流
            {
                fs.Write(bytes, 0, writeLength);//追加写入文件
                contentLength -= writeLength;
                if (contentLength == 0)//如果写入完成 给出提示
                    MessageBox.Show("下载完成");
            }
        }
    }
}

 

2、异步下载

//开启一个异步线程
await Task.Run(async () =>
{
    //异步操作UI元素
    label1.Invoke((Action)(() =>
    {
        label1.Text = "准备下载...";
    }));

    long downloadSize = 0;//已经下载大小
    long downloadSpeed = 0;//下载速度
    using (HttpClient http = new HttpClient())
    {
        var httpResponseMessage = await http.GetAsync("http://localhost:8088/wms_manual.pdf", HttpCompletionOption.ResponseHeadersRead);//发送请求
        var contentLength = httpResponseMessage.Content.Headers.ContentLength;   //文件大小
                                                                                 //
        using (var stream = await httpResponseMessage.Content.ReadAsStreamAsync())
        {
            var readLength = 1024000;//1000K
            byte[] bytes = new byte[readLength];
            int writeLength;
            var beginSecond = DateTime.Now.Second;//当前时间秒
            while ((writeLength = stream.Read(bytes, 0, readLength)) > 0)
            {
                //使用追加方式打开一个文件流
                using (FileStream fs = new FileStream(Application.StartupPath + "/temp.rar", FileMode.Append, FileAccess.Write))
                {
                    fs.Write(bytes, 0, writeLength);
                }
                downloadSize += writeLength;
                downloadSpeed += writeLength;
                progressBar1.Invoke((Action)(() =>
                {
                    var endSecond = DateTime.Now.Second;
                    if (beginSecond != endSecond)//计算速度
                    {
                        downloadSpeed = downloadSpeed / (endSecond - beginSecond);
                        label1.Text = "下载速度" + downloadSpeed / 1024 + "KB/S";

                        beginSecond = DateTime.Now.Second;
                        downloadSpeed = 0;//清空
                    }
                    progressBar1.Value = Math.Max((int)(downloadSize * 100 / contentLength), 1);
                }));
            }

            label1.Invoke((Action)(() =>
            {
                label1.Text = "下载完成";
            }));
        }
    }
});

 

3、断点续传

/// <summary>
/// 是否暂停
/// </summary>
static bool isPause = true;
/// <summary>
/// 下载开始位置（也就是已经下载了的位置）
/// </summary>
static long rangeBegin = 0;//(当然，这个值也可以存为持久化。如文本、数据库等)

/// <summary>
/// 断线续传
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private async void button3_ClickAsync(object sender, EventArgs e)
{
    isPause = !isPause;
    if (!isPause)//点击下载
    {
        button3.Text = "暂停";

        await Task.Run(async () =>
        {
            //异步操作UI元素
            label1.Invoke((Action)(() =>
           {
               label1.Text = "准备下载...";
           }));

            long downloadSpeed = 0;//下载速度
            using (HttpClient http = new HttpClient())
            {
                //var url = "http://localhost:813/新建文件夹2.rar";  //a标签下载链接
                var url = "http://localhost:8088/wms_manual.pdf";    //我们自己实现的服务端下载链接
                var request = new HttpRequestMessage { RequestUri = new Uri(url) };
                request.Headers.Range = new RangeHeaderValue(rangeBegin, null);//【关键点】全局变量记录已经下载了多少，然后下次从这个位置开始下载。
                var httpResponseMessage = await http.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);
                var contentLength = httpResponseMessage.Content.Headers.ContentLength;//本次请求的内容大小
                if (httpResponseMessage.Content.Headers.ContentRange != null) //如果为空，则说明服务器不支持断点续传
                {
                    contentLength = httpResponseMessage.Content.Headers.ContentRange.Length;//服务器上的文件大小
                }

                using (var stream = await httpResponseMessage.Content.ReadAsStreamAsync())
                {
                    var readLength = 1024000;//1000K
                    byte[] bytes = new byte[readLength];
                    int writeLength;
                    var beginSecond = DateTime.Now.Second;//当前时间秒
                    while ((writeLength = stream.Read(bytes, 0, readLength)) > 0 && !isPause)
                    {
                        //使用追加方式打开一个文件流
                        using (FileStream fs = new FileStream(Application.StartupPath + "/temp.rar", FileMode.Append, FileAccess.Write))
                        {
                            fs.Write(bytes, 0, writeLength);
                        }
                        downloadSpeed += writeLength;
                        rangeBegin += writeLength;
                        progressBar1.Invoke((Action)(() =>
                        {
                            var endSecond = DateTime.Now.Second;
                            if (beginSecond != endSecond)//计算速度
                            {
                                downloadSpeed = downloadSpeed / (endSecond - beginSecond);
                                label1.Text = "下载速度" + downloadSpeed / 1024 + "KB/S";

                                beginSecond = DateTime.Now.Second;
                                downloadSpeed = 0;//清空
                            }
                            progressBar1.Value = Math.Max((int)((rangeBegin) * 100 / contentLength), 1);
                        }));
                    }

                    if (rangeBegin == contentLength)
                    {
                        label1.Invoke((Action)(() =>
                        {
                            label1.Text = "下载完成";
                        }));
                    }
                }
            }
        });
    }
    else//点击暂停
    {
        button3.Text = "继续下载";
        label1.Text = "暂停下载";
    }
}

 

 

4、多线程下载文件

/// <summary>
/// 多线程下载文件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private async void button4_ClickAsync(object sender, EventArgs e)
{
    using (HttpClient http = new HttpClient())
    {
        var url = "http://localhost:8088/wms_manual.pdf";
        var httpResponseMessage = await http.GetAsync(url, HttpCompletionOption.ResponseHeadersRead);
        var contentLength = httpResponseMessage.Content.Headers.ContentLength.Value;
        var size = contentLength / 10; //这里为了方便，就直接分成10个线程下载。（当然这是不合理的）
        var tasks = new List<Task>();
        for (int i = 0; i < 10; i++)
        {
            var begin = i * size;
            var end = begin + size - 1;
            var task = FileDownload(url, begin, end, i);
            tasks.Add(task);
        }
        for (int i = 0; i < 10; i++)
        {
            await tasks[i];  //当然，这里如有下载异常没有考虑、文件也没有校验。各位自己完善吧。
            progressBar1.Value = (i + 1) * 10;
        }
        FileMerge(Application.StartupPath + @"\File", "temp.rar");
        label1.Text = "下载完成";
    }
}

/// <summary>
/// 文件下载
/// （如果你有兴趣，可以没个线程弄个进度条）
/// </summary>
/// <param name="begin"></param>
/// <param name="end"></param>
/// <param name="index"></param>
/// <returns></returns>
public Task FileDownload(string url, long begin, long end, int index)
{
    var task = Task.Run(async () =>
    {
        using (HttpClient http = new HttpClient())
        {
            var request = new HttpRequestMessage { RequestUri = new Uri(url) };
            request.Headers.Range = new RangeHeaderValue(begin, end);//【关键点】全局变量记录已经下载了多少，然后下次从这个位置开始下载。
            var httpResponseMessage = await http.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

            using (var stream = await httpResponseMessage.Content.ReadAsStreamAsync())
            {
                var readLength = 1024000;//1000K
                byte[] bytes = new byte[readLength];
                int writeLength;
                var beginSecond = DateTime.Now.Second;//当前时间秒
                var filePaht = Application.StartupPath + "/File/";
                if (!Directory.Exists(filePaht))
                    Directory.CreateDirectory(filePaht);

                try
                {
                    while ((writeLength = stream.Read(bytes, 0, readLength)) > 0)
                    {
                        //使用追加方式打开一个文件流
                        using (FileStream fs = new FileStream(filePaht + index, FileMode.Append, FileAccess.Write))
                        {
                            fs.Write(bytes, 0, writeLength);
                        }
                    }
                }
                catch (Exception)
                {
                    //如果出现异常则删掉这个文件
                    File.Delete(filePaht + index);
                }
            }
        }
    });

    return task;
}

/// <summary>
/// 合并文件
/// </summary>
/// <param name="path"></param>
/// <returns></returns>
public bool FileMerge(string path, string fileName)
{
    //这里排序一定要正确，转成数字后排序（字符串会按1 10 11排序，默认10比2小）
    foreach (var filePath in Directory.GetFiles(path).OrderBy(t => int.Parse(Path.GetFileNameWithoutExtension(t))))
    {
        using (FileStream fs = new FileStream(Directory.GetParent(path).FullName + @"\" + fileName, FileMode.Append, FileAccess.Write))
        {
            byte[] bytes = System.IO.File.ReadAllBytes(filePath);//读取文件到字节数组
            fs.Write(bytes, 0, bytes.Length);//写入文件
        }
        System.IO.File.Delete(filePath);
    }
    Directory.Delete(path);
    return true;
}

 

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