使用 WebClient() 计算要下载的总字节数 [英] Calculating total bytes to download using WebClient()
本文介绍了使用 WebClient() 计算要下载的总字节数的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
变量totalBytes"始终为 -1,因此我无法正确计算/更新进度条,为什么会发生这种情况?
The variable 'totalBytes' is constantly at -1 so I cannot calculate/update the progress bar correctly, why would this be happening?
private void button1_Click(object sender, EventArgs e)
{
WebClient client = new WebClient();
client.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);
client.DownloadFileAsync(new Uri("http://example.com/test.mp3"), @"E:\Test.mp3");
}
private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
double bytesIn = double.Parse(e.BytesReceived.ToString());
label1.Text = Convert.ToString(bytesIn);
double totalBytes = double.Parse(e.TotalBytesToReceive.ToString()); //stays at -1
label2.Text = Convert.ToString(totalBytes);
double percentage = bytesIn / totalBytes * 100;
label3.Text = Convert.ToString(percentage);
progressBar1.Value = int.Parse(Math.Truncate(percentage).ToString());
}
推荐答案
A WebClient
在内部使用了一个 WebRequest
,问题很可能是你下载的服务器文件来自不发送 Content-Length
HTTP 标头,在这种情况下,您应该使用 Indeterminate
ProgressBar 样式(例如 Marquee).
A WebClient
uses a WebRequest
internally, and the problem is likely that the server you are downloading the file from is not sending the Content-Length
HTTP header, in which case you should use a Indeterminate
ProgressBar style (eg. Marquee).
这篇关于使用 WebClient() 计算要下载的总字节数的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文