如何使用webclient計算和顯示下載速度？

目標是在下載時計算并在 label4.Text 上顯示下載速度。

private void Download()
        {
            using (var client = new WebClient())
            {
                client.DownloadFileCompleted  = (s, e) => label1.Text = "Download file completed.";
                client.DownloadProgressChanged  = (s, e) => progressBar1.Value = e.ProgressPercentage;
                client.DownloadProgressChanged  = (s, e) => label2.Text = FormatBytes(e.BytesReceived);
                client.DownloadProgressChanged  = (s, e) => label4.Text = e.
                client.DownloadProgressChanged  = (s, e) =>
                {
                    label3.Text = "%"   e.ProgressPercentage.ToString();
                    label3.Left = Math.Min(
                        (int)(progressBar1.Left   e.ProgressPercentage / 100f * progressBar1.Width),
                        progressBar1.Width - label3.Width
                    );                   
                };

                client.DownloadFileAsync(new Uri("https://speed.hetzner.de/10GB.bin"), @"d:\10GB.bin");
            }
        } 

在帶有 label4.Text 的那一行，我想顯示速度。

client.DownloadProgressChanged  = (s, e) => label4.Text = e.

uj5u.com熱心網友回復：

正如@AKX建議的那樣，Stopwatch類可以幫助您計算下載檔案時每秒接收的位元組數。

在類范圍內創建一個欄位（基于 WPF 應用程式的示例）：

public partial class MainWindow : Window 
{
    private readonly System.Diagnostics.Stopwatch stopwatch = new System.Diagnostics.Stopwatch();
}

初始化時WebClient（以最簡單的方式），創建 2 個處理程式：for WebClient.DownloadProgressChangedevent 和 for WebClient.DownloadFileCompletedevent。然后呼叫之前WebClient.DownloadFileAsync()呼叫stopwatch.Start()開始計時。

using (System.Net.WebClient wc = new System.Net.WebClient())
{
    wc.DownloadProgressChanged  = OnDownloadProgressChange;
    wc.DownloadFileCompleted  = OnDownloadFileComplete;

    stopwatch.Start(); // Start the Stopwatch
    wc.DownloadFileAsync(downloadLink, fileName); // Run file download asynchroniously
}

在DownloadProgressChanged事件處理程式中，您可以結合DownloadProgressChangedEventArgs's BytesReceivedproperty 和Stopwatch's Elapsed.TotalSecondsproperty 來獲得下載速度：

private void OnDownloadProgressChange(object sender, System.Net.DownloadProgressChangedEventArgs e)
{
    // Calculate progress values
    string downloadSpeed = string.Format("{0} MB/s", (e.BytesReceived / 1024.0 / 1024.0 / stopwatch.Elapsed.TotalSeconds).ToString("0.00"));
}

我將BytesReceived兩次除以 1024 以獲得以 MB 而不是位元組為單位的值，但您可以根據需要進行選擇。我也將結果值格式化為0.00（例如獲得“1.23 MB/s”）。DownloadProgressChangedEventArgs如果需要，您還可以為您的目的計算和格式化其他屬性。

最后，在WebClient.DownloadFileCompleted事件處理程式中，您應該重置Stopwatch以停止它并為其他新下載重置其測量時間：

private void OnDownloadFileComplete(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
{
    stopwatch.Reset();
}

完整版本可能如下所示 ( MainWindow.cs)：

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private readonly System.Diagnostics.Stopwatch stopwatch = new System.Diagnostics.Stopwatch();

    private void BtnDownloadFile_Click(object sender, RoutedEventArgs e)
    {
        Uri downloadLink = new Uri("https://speed.hetzner.de/100MB.bin");
        string fileName = "H:\\100MB.bin";

        btnDownloadFile.IsEnabled = false; // Disable to prevent multiple runs

        using (System.Net.WebClient wc = new System.Net.WebClient())
        {
            wc.DownloadProgressChanged  = OnDownloadProgressChange;
            wc.DownloadFileCompleted  = OnDownloadFileComplete;

            stopwatch.Start();
            wc.DownloadFileAsync(downloadLink, fileName);
        }
    }

    private void OnDownloadProgressChange(object sender, System.Net.DownloadProgressChangedEventArgs e)
    {
        // Calculate progress values
        string downloadProgress = e.ProgressPercentage   "%";
        string downloadSpeed = string.Format("{0} MB/s", (e.BytesReceived / 1024.0 / 1024.0 / stopwatch.Elapsed.TotalSeconds).ToString("0.00"));
        string downloadedMBs = Math.Round(e.BytesReceived / 1024.0 / 1024.0)   " MB";
        string totalMBs = Math.Round(e.TotalBytesToReceive / 1024.0 / 1024.0)   " MB";

        // Format progress string
        string progress = $"{downloadedMBs}/{totalMBs} ({downloadProgress}) @ {downloadSpeed}"; // 10 MB / 100 MB (10%) @ 1.23 MB/s

        // Set values to contols
        lblProgress.Content = progress;
        progBar.Value = e.ProgressPercentage;
    }

    private void OnDownloadFileComplete(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
    {
        lblProgress.Content = "Download complete!";
        stopwatch.Reset();
        btnDownloadFile.IsEnabled = true; // Restore arailability of download button
    }
}

XAML：

<Grid>
    <StackPanel HorizontalAlignment="Stretch" 
                VerticalAlignment="Center">
        <Label x:Name="lblProgress" 
               Content="Here would be progress text" 
               Margin="10,0,10,5" 
               HorizontalContentAlignment="Center"/>
        <ProgressBar x:Name="progBar" 
                     Height="20" 
                     Margin="10,0,10,5" />
        <Button x:Name="btnDownloadFile" 
                Content="Download file" 
                Width="175" 
                Height="32" 
                Click="BtnDownloadFile_Click"/>
    </StackPanel>
</Grid>

看起來如何：

標籤：C＃ 统一3d

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