当文件下载完成时，我如何知道使用httpwebrequest和webresponse？

using System;
using System.IO;
using System.Net;

public class FileDownloader
{
    public static void Main(string[] args)
    {
        string fileUrl = "http://example.com/file.txt";
        string savePath = "C:\\Downloads\\file.txt";

        DownloadFile(fileUrl, savePath);
    }

    public static void DownloadFile(string fileUrl, string savePath)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(fileUrl);
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();

        long fileSize = response.ContentLength;
        byte[] buffer = new byte[4096];
        int bytesRead = 0;
        long totalBytesRead = 0;

        using (Stream responseStream = response.GetResponseStream())
        {
            using (FileStream fileStream = File.Create(savePath))
            {
                while ((bytesRead = responseStream.Read(buffer, 0, buffer.Length)) > 0)
                {
                    fileStream.Write(buffer, 0, bytesRead);
                    totalBytesRead += bytesRead;

                    // 判断下载进度
                    Console.WriteLine("Downloaded {0} bytes out of {1}", totalBytesRead, fileSize);
                }
            }
        }

        Console.WriteLine("File downloaded successfully.");
    }
}