驗證文件存在於網站上

我正在嘗試做一個簡單的函數來驗證網站上是否存在特定的文件。驗證文件存在於網站上

web請求被設置爲頭這樣我就可以得到，而不是將整個文件下載文件長度，但我得到「無法連接到遠程服務器」異常。如何驗證網站上存在的文件？

WebRequest w; 

    WebResponse r; 

    w = WebRequest.Create("http://website.com/stuff/images/9-18-2011-3-42-16-PM.gif"); 
    w.Method = "HEAD"; 
    r = w.GetResponse();

編輯：我的壞，事實證明我檢查日誌後我的防火牆阻止http請求。它沒有提示我一個例外規則，所以我認爲這是一個錯誤。

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2011-09-18 Drake

你知不知道你在說Web服務器是否真正支持HEAD請求？您是否嘗試過使用Wireshark來查看網絡級別發生了什麼？ –

我剛剛使用隨機URL測試了您的代碼片段，並且它可以正常工作。你確定你指定的網址實際上存在嗎？ –

我同意@Jon，OP應該用GET替代來看看會發生什麼。 –

try 
{ 
    WebRequest request = HttpWebRequest.Create("http://www.microsoft.com/NonExistantFile.aspx"); 
    request.Method = "HEAD"; // Just get the document headers, not the data. 
    request.Credentials = System.Net.CredentialCache.DefaultCredentials; 
    // This may throw a WebException: 
    using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) 
    { 
     if (response.StatusCode == HttpStatusCode.OK) 
     { 
      // If no exception was thrown until now, the file exists and we 
      // are allowed to read it. 
      MessageBox.Show("The file exists!"); 
     } 
     else 
     { 
      // Some other HTTP response - probably not good. 
      // Check its StatusCode and handle it. 
     } 
    } 
} 
catch (WebException ex) 
{ 
    // Cast the WebResponse so we can check the StatusCode property 
    HttpWebResponse webResponse = (HttpWebResponse)ex.Response; 

    // Determine the cause of the exception, was it 404? 
    if (webResponse.StatusCode == HttpStatusCode.NotFound) 
    { 
     MessageBox.Show("The file does not exist!"); 
    } 
    else 
    { 
     // Handle differently... 
     MessageBox.Show(ex.Message); 
    } 
}

來源

2011-09-18 21:42:10 meziantou

我測試過這一點，它工作正常：

private bool testRequest(string urlToCheck) 
{ 
    var wreq = (HttpWebRequest)WebRequest.Create(urlToCheck); 

    //wreq.KeepAlive = true; 
    wreq.Method = "HEAD"; 

    HttpWebResponse wresp = null; 

    try 
    { 
     wresp = (HttpWebResponse)wreq.GetResponse(); 

     return (wresp.StatusCode == HttpStatusCode.OK); 
    } 
    catch (Exception exc) 
    { 
     System.Diagnostics.Debug.WriteLine(String.Format("url: {0} not found", urlToCheck)); 
     return false; 
    } 
    finally 
    { 
     if (wresp != null) 
     { 
      wresp.Close(); 
     } 
    } 
}

試試這個網址：http://www.centrosardegna.com/images/losa/losaabbasanta.png然後修改圖像名稱，它會返回false。 ;-)

來源

2011-09-18 21:42:24

驗證文件存在於網站上

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