C#使用HtmlAgilityPack获取加密货币实时价始终返回首次值如何解决

算力阿峰

2026-10-3

问题修复方案

核心原因

WebClient默认启用本地请求缓存，相同URL的重复请求会优先读取首次拉取的本地缓存，不会发起新的网络请求获取最新页面内容
目标站点对缺省标准请求头的请求会返回固定缓存内容，不会返回实时更新的页面数据

修复后的代码

private void button1_Click(object sender, EventArgs e)
{
    timer1.Start();
}

private void timer1_Tick(object sender, EventArgs e)
{
    Uri url = new Uri("https://www.bloomberght.com/borsa");
    WebClient client = new WebClient();
    // 禁用WebClient缓存
    client.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.NoCacheNoStore);
    // 添加标准浏览器请求头，避免站点返回缓存内容
    client.Headers.Add("user-agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36");
    client.Encoding = System.Text.Encoding.UTF8;
    string html = client.DownloadString(url);
    HtmlAgilityPack.HtmlDocument document = new HtmlAgilityPack.HtmlDocument();
    document.LoadHtml(html);
    HtmlNodeCollection nodes = document.DocumentNode.SelectNodes("//a[@id='dolar']/span[@class='data-info']/small[@data-type='son_fiyat']");

    foreach (var item in nodes)
    {
        label1.Text = item.InnerText;
        listBox1.Items.Add(item.InnerText);
    }
    // 释放WebClient资源避免内存泄漏
    client.Dispose();
}