从上面我猜你在别的地方有问题。你能在服务器端记录http请求吗?当你改变一些随机种子参数时你会得到什么?

也许服务器缓存文件(如果日志显示请求确实每分钟都被触发)。

你用ISA还是SQUID?

我知道用答案回答可能不受欢迎,但评论不允许我这么多的文字:)

编辑:

不管怎样,使用 HttpRequest WebClient ,希望(如果你怀疑 网络客户端 )一切都会解决的。如果不解决的话 HttpRequest请求

进一步完善:

再低一点: How do I Create an HTTP Request Manually in .Net?

你可以尝试附加一些 作为查询字符串的一部分,将随机数添加到您的url

对于前-

Random random = new Random();
string url = originalUrl + "?random=" + random.Next().ToString();
webclient.DownloadFile(url, downloadedfileurl);

NoCacheNoStore :

client.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.NoCacheNoStore); 

在某些情况下,网络调试软件可能会导致此问题。为了确保您的url没有被缓存,您可以附加一个随机数作为最后一个参数,以使url唯一。在大多数情况下,此随机参数被服务器忽略(服务器尝试读取作为名称-值对发送的参数)。

http://www.someserver.com/?param1=val1&ThisIsRandom=RandomValue

我在使用webClient的powershell中遇到了类似的问题,在切换到使用webRequest之后也出现了这个问题。我发现socket是重用的,这会导致各种各样的服务器/网络端缓存(在我的例子中,负载均衡器也会妨碍使用https,尤其是https)。解决方法是在webrequest对象中禁用keepalive和可能的管道,如下所示,这将强制每个请求使用一个新的套接字:

#Define Funcs Function httpRequest {
     param([string]$myurl)
     $r = [System.Net.WebRequest]::Create($myurl)
     $r.keepalive = 0
     $sr = new-object System.IO.StreamReader (($r.GetResponse()).GetResponseStream())
     $sr.ReadToEnd() }

    WebRequest request = WebRequest.Create(uri);
     // Define a cache policy for this request only. 
     HttpRequestCachePolicy noCachePolicy = new HttpRequestCachePolicy(HttpRequestCacheLevel.NoCacheNoStore);
     request.CachePolicy = noCachePolicy;
     WebResponse response = request.GetResponse();

//below is the function for downloading the file

   public static int DownloadFile(String remoteFilename,
                           String localFilename)
    {
        // Function will return the number of bytes processed
        // to the caller. Initialize to 0 here.
        int bytesProcessed = 0;

        // Assign values to these objects here so that they can
        // be referenced in the finally block
        Stream remoteStream = null;
        Stream localStream = null;
        WebResponse response = null;

        // Use a try/catch/finally block as both the WebRequest and Stream
        // classes throw exceptions upon error
        try
        {
            // Create a request for the specified remote file name
            WebRequest request = WebRequest.Create(remoteFilename);
            // Define a cache policy for this request only. 
            HttpRequestCachePolicy noCachePolicy = new HttpRequestCachePolicy(HttpRequestCacheLevel.NoCacheNoStore);
            request.CachePolicy = noCachePolicy;
            if (request != null)
            {
                // Send the request to the server and retrieve the
                // WebResponse object 
                response = request.GetResponse();

                if (response != null)
                {
                    if (response.IsFromCache)
                        //do what you want

                    // Once the WebResponse object has been retrieved,
                    // get the stream object associated with the response's data
                    remoteStream = response.GetResponseStream();

                    // Create the local file
                    localStream = File.Create(localFilename);

                    // Allocate a 1k buffer
                    byte[] buffer = new byte[1024];
                    int bytesRead;

                    // Simple do/while loop to read from stream until
                    // no bytes are returned
                    do
                    {
                        // Read data (up to 1k) from the stream
                        bytesRead = remoteStream.Read(buffer, 0, buffer.Length);

                        // Write the data to the local file
                        localStream.Write(buffer, 0, bytesRead);

                        // Increment total bytes processed
                        bytesProcessed += bytesRead;
                    } while (bytesRead > 0);
                }
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            // Close the response and streams objects here 
            // to make sure they're closed even if an exception
            // is thrown at some point
            if (response != null) response.Close();
            if (remoteStream != null) remoteStream.Close();
            if (localStream != null) localStream.Close();
        }

        // Return total bytes processed to caller.
        return bytesProcessed;
    }

client.CachePolicy = new RequestCachePolicy(RequestCacheLevel.BypassCache);

应该有用。只需确保清除缓存并删除Internet Explorer中所有临时下载的文件 之前 System.Net 和IE使用相同的缓存。

使用 HTTPRequest "no-cache" 但所有这些标题:

<meta http-equiv="Cache-control" content="no-cache">
<meta http-equiv="Cache-control" content="no-store">
<meta http-equiv="Pragma" content="no-cache">
<meta http-equiv="Expires" content="-1">

在IE11中,它对我不起作用,直到我包括了最后两个中的一个或两个。

如果一个网页曾经被访问,现在从服务器上删除,方法HttpWebResponse.GetResponse文件()将为缓存副本提供一个响应,以“在经过足够的时间之前,或者您重新启动计算机,它将不会触发404页未找到错误的预期异常,您现在无法知道该网页现在根本不存在。

• 将标题设置为(“缓存控制”、“无缓存”)
• “设置”请求缓存策略到“noCachePolicy”
• 使用不带路由器的有线互联网。。。。。。。。。。不起作用!

HttpWebResponse.GetResponse() 会给你一个新的页面来反映变化。

请检查您是否受到费率限制!我从nginx服务器上取回这个:

403禁止

这是我使用的程序(C#)

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DownloadFile();
            Console.ReadLine();
        }

        public static void DownloadFile()
        {
            var downloadedDatabaseFile = Path.Combine(Path.GetTempPath(), Path.GetTempFileName());
            Console.WriteLine(downloadedDatabaseFile);

            var client = new WebClient();
            client.DownloadProgressChanged += (sender, args) =>
            {
                Console.WriteLine("{0} of {1} {2}%", args.BytesReceived, args.TotalBytesToReceive, args.ProgressPercentage);
            };

            client.DownloadFileCompleted += (sender, args) =>
            {
                Console.WriteLine("Download file complete");

                if (args.Error != null)
                {
                    Console.WriteLine(args.Error.Message);
                }
            };

            client.DownloadFileAsync(new Uri("http://geolite.maxmind.com/download/geoip/database/GeoLiteCity.dats.gz"), downloadedDatabaseFile);
        }
    }
}

控制台打印出:

C:\Users\jake.scott.WIN-J8OUFV09HQ8\AppData\Local\Temp\2\tmp7CA.tmp
Download file complete
The remote server returned an error: (403) Forbidden.

因为我用的是:

wclient.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.NoCacheNoStore);
wclient.Headers.Add("Cache-Control", "no-cache");

我再也没有缓存文件了。

private void del_IE_files()
{
    string path = Environment.GetFolderPath(Environment.SpecialFolder.InternetCache);
    //for deleting files

    System.IO.DirectoryInfo DInfo = new DirectoryInfo(path);
    FileAttributes Attr = DInfo.Attributes;
    DInfo.Attributes = FileAttributes.Normal;

    foreach (FileInfo file in DInfo.GetFiles())
    {
        file.Delete();
    }

    foreach (DirectoryInfo dir in DInfo.GetDirectories())
    {
        try
        {
            dir.Delete(true); //delete subdirectories and files
        }
        catch
        {

        }
    }
}

如果您可以访问Web服务器,请打开Internet Explorer转到

Internet Explorer -> Internet Options -> Browsing History "Settings" -> Temporary Internet Files "never"

清除浏览器缓存,瞧,它会工作的!