如何以C＃编程方式下载大文件 [英] How to programmatically download a large file in C#

问题描述

在处理之前，我需要以编程方式下载大型文件。最好的方法是什么？由于文件大，我想要具体时间等待，以便我可以强制退出。

I need to programmatically download a large file before processing it. What's the best way to do that? As the file is large, I want to specific time to wait so that I can forcefully exit.

我知道WebClient.DownloadFile（）。但是，似乎没有一种方式来确定一段时间来等待强制退出。

I know of WebClient.DownloadFile(). But there does not seem a way to specific an amount of time to wait so as to forcefully exit.

try
{
    WebClient client = new WebClient();
    Uri uri = new Uri(inputFileUrl);
    client.DownloadFile(uri, outputFile);
}
catch (Exception ex)
{
    throw;
}

另一种方法是使用命令行实用程序（wget）下载文件并使用ProcessStartInfo触发命令，并使用进程'WaitForExit（int ms）强制退出。

Another way is to use a command line utility (wget) to download the file and fire the command using ProcessStartInfo and use Process' WaitForExit(int ms) to forcefully exit.

ProcessStartInfo startInfo = new ProcessStartInfo();
//set startInfo object

try
{
    using (Process exeProcess = Process.Start(startInfo))
    {
        //wait for time specified
        exeProcess.WaitForExit(1000 * 60 * 60);//wait till 1m

        //check if process has exited
        if (!exeProcess.HasExited)
        {
            //kill process and throw ex
            exeProcess.Kill();
            throw new ApplicationException("Downloading timed out");
        }
    }
}
catch (Exception ex)
{
    throw;
}

有更好的方法吗？请帮忙。谢谢。

Is there a better way? Please help. Thanks.

推荐答案

使用 WebRequest 并获取响应流。然后从响应流块的字节读取，并将每个块写入目标文件。这样，您可以控制何时停止下载时间太长，因为您可以控制块之间，您可以根据时钟决定下载是否已超时：      

Use a WebRequest and get the response stream. Then read from the reponse Stream blocks of bytes, and write each block to the destination file. This way you can control when to stop if the download takes too long, as you get control between chunks and you can decide if the download has timed out based on a clock:       

        DateTime startTime = DateTime.UtcNow;
        WebRequest request = WebRequest.Create("http://www.example.com/largefile");
        WebResponse response = request.GetResponse();
        using (Stream responseStream = response.GetResponseStream()) {
            using (Stream fileStream = File.OpenWrite(@"c:\temp\largefile")) { 
                byte[] buffer = new byte[4096];
                int bytesRead = responseStream.Read(buffer, 0, 4096);
                while (bytesRead > 0) {       
                    fileStream.Write(buffer, 0, bytesRead);
                    DateTime nowTime = DateTime.UtcNow;
                    if ((nowTime - startTime).TotalMinutes > 5) {
                        throw new ApplicationException(
                            "Download timed out");
                    }
                    bytesRead = responseStream.Read(buffer, 0, 4096);
                }
            }
        }

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