HttpWebRequest引發“ 404遠程服務器返回錯誤：（404）未找到。”

Question

我正在嘗試發出網絡請求：

String url = @"http://stackoverflow.com/aaaaaaaa.html";

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

String responseText;

using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
   if (response.StatusCode == HttpStatusCode.NotFound) //404
      return "";

   using (StreamReader responseStream = new StreamReader(response.GetResponseStream()))
   {
      responseText = responseStream.ReadToEnd();
   }
}

問題是該行：

request.GetResponse();

引發異常：

• System.Net.HttpWebResponse
  • “遠程服務器返回錯誤：（404）找不到。”

為什么HttpWebRequest拋出異常？ 以及我如何使其停止？

或者

有人可以建議一種方法或.NET類，該方法或類可以讓我與網絡服務器進行通訊，並檢索完全有效的但並不例外的 404。

HttpClient有其自身的問題 ，因此無需考慮。

Answer 1

這是我之前編寫的一些代碼，歡迎您使用該代碼處理這種情況。 如果引發異常，則可以通過捕獲WebException來獲取狀態代碼。

public class WebResult
{
    public string Response { get; set; }
    public bool WasSuccessful { get; set; }
    public HttpStatusCode? StatusCode { get; set; }
}

public WebResult GetUrlContents(string url)
{
    try
    {
        var request = (HttpWebRequest)WebRequest.Create(url);

        using (var response = (HttpWebResponse)request.GetResponse())
        using (var responseStream = new StreamReader(response.GetResponseStream()))
        {
            return new WebResult
            {
                WasSuccessful = true,
                Response = responseStream.ReadToEnd(),
                StatusCode = response.StatusCode
            };
        }
    }
    catch (WebException webException)
    {
        return new WebResult
        {
            Response = null,
            WasSuccessful = false,
            StatusCode = (webException.Response as HttpWebResponse)?.StatusCode
        };
    }
}