.NET 中的 WebRequest 异常

Question

我使用此代码片段来验证 URL 中指定的文件是否存在，并每隔几秒为每个用户尝试一次。有时（主要是当有大量用户使用该网站时）代码不起作用。

    [WebMethod()]
    public static string GetStatus(string URL)
    {
        bool completed = false;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);

        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {
            try
            {
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    completed = true;
                }
            }
            catch (Exception)
            {
                //Just don't do anything. Retry after few seconds
            }
        }

        return completed.ToString();
    }

当我查看 Windows 事件日志时，发现了几个错误：

Unable to read data from the transport connection. An existing connection was forcibly closed

The Operation has timed out

The remote host closed the connection. The error code is 0x800703E3

当我重新启动 IIS 时，一切正常，直到下次发生这种情况。

Answer 1

您将 try/catch 放入 using 语句中，而 request.GetResponse 方法可能会抛出：

bool completed = false;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
try
{
    using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
    {
        if (response.StatusCode == HttpStatusCode.OK)
        {
            completed = true;
        }
    }
}
catch (Exception)
{
    //Just don't do anything. Retry after few seconds
}
return completed.ToString();