Question

我知道我可以在我的文件系统上本地检查文件是否存在：

if(File.Exists(path))

我可以查看特定的远程网址吗？

Answer 1

如果您尝试验证是否存在网络资源，我建议您使用HttpWebRequest课程。这样，您就可以向相关网址发送HEAD个请求。即使资源存在，也只返回响应头。

var url = "http://www.domain.com/image.png";
HttpWebResponse response = null;
var request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "HEAD";


try
{
    response = (HttpWebResponse)request.GetResponse();
}
catch (WebException ex)
{
    /* A WebException will be thrown if the status of the response is not `200 OK` */
}
finally
{
    // Don't forget to close your response.
    if (response != null)
    {
        response.Close();
    }
}

当然，如果要下载资源（如果存在），则发送GET请求的效率可能更高（通过不将Method属性设置为"HEAD" ，或使用WebClient类）。

Answer 2

如果你想复制＆amp;粘贴 Justin 的代码并获取使用方法，以下是我实施的方法：

using System.Net;

public class MyClass {
    static public bool URLExists (string url) {
        bool result = false;

        WebRequest webRequest = WebRequest.Create(url);
        webRequest.Timeout = 1200; // miliseconds
        webRequest.Method = "HEAD";

        HttpWebResponse response = null;

        try {
            response = (HttpWebResponse)webRequest.GetResponse();
            result = true;
        } catch (WebException webException) {
            Debug.Log(url +" doesn't exist: "+ webException.Message);
        } finally {
            if (response != null) {
                response.Close();
            }
        }

        return result;
    }
}

我会保持他的观察：

如果您要下载该资源，并且该资源存在，则通过不将GET属性设置为Method或使用以下内容来发送"HEAD"请求会更高效WebClient上课。

Answer 3

以下是代码的简化版本：

public bool URLExists(string url)
{
    bool result = true;

    WebRequest webRequest = WebRequest.Create(url);
    webRequest.Timeout = 1200; // miliseconds
    webRequest.Method = "HEAD";

    try
    {
        webRequest.GetResponse();
    }
    catch
    {
        result = false;
    }

    return result;
}

Answer 4

如果您正在使用unc路径或映射驱动器，这将正常工作。

如果您使用的是网址（http，ftp等），最好使用WebClient - 如果不存在，您将收到WebException。

Answer 5

public static bool UrlExists(string file)
    {
        bool exists = false;
        HttpWebResponse response = null;
        var request = (HttpWebRequest)WebRequest.Create(file);
        request.Method = "HEAD";
        request.Timeout = 5000; // milliseconds
        request.AllowAutoRedirect = false;

        try
        {
            response = (HttpWebResponse)request.GetResponse();
            exists = response.StatusCode == HttpStatusCode.OK;
        }
        catch
        {
            exists = false;
        }
        finally
        {
            // close your response.
            if (response != null)
                response.Close();
        }
        return exists;
    }

Answer 6

我在asp.net核心中有相同的问题要解决，我已经使用HttpClient解决了

private async Task<bool> isFileExist(string url)
        {
            using (HttpClient client = new HttpClient())
            {
                var restponse = await client.GetAsync(url);

               return restponse.StatusCode == System.Net.HttpStatusCode.OK;
            }
        }

Answer 7

我的版本：

    public bool IsUrlExist(string url, int timeOutMs = 1000)
    {
        WebRequest webRequest = WebRequest.Create(url);
        webRequest.Method = "HEAD";
        webRequest.Timeout = timeOut;

        try
        {
            var response = webRequest.GetResponse();
            /* response is `200 OK` */
            response.Close();
        }
        catch
        {
            /* Any other response */
            return false;
        }

        return true;
    }

Answer 8

WebRequest将等待很长时间（忽略超时用户设置），因为没有设置代理，所以我改为使用RestSharp来执行此操作。

var client = new RestClient(url);
var request = new RestRequest(Method.HEAD);

 request.Timeout = 5000;
 var response = client.Execute(request);
 result = response.StatusCode == HttpStatusCode.OK;

Answer 9

感谢所有答案。而且我想添加我的实现，其中包括在遇到错误时针对默认情况（例如我的情况）的默认状态。

private bool HTTP_URLExists(String vstrURL, bool vResErrorDefault = false, int vTimeOut = 1200)
{
   bool vResult = false;
   WebRequest webRequest = WebRequest.Create(vstrURL);
   webRequest.Timeout = vTimeOut; // miliseconds
   webRequest.Method = "HEAD";
   HttpWebResponse response = null;
   try
   {
      response = (HttpWebResponse)webRequest.GetResponse();
      if (response.StatusCode == HttpStatusCode.OK) vResult = true;
      else if (response.StatusCode == HttpStatusCode.NotFound) vResult = false;
      else vResult = vResErrorDefault;
   }
       catch (WebException ex)
           {
           
              if (ex.Status == WebExceptionStatus.ProtocolError && ex.Response != null)
              {
                  var resp01 = (HttpWebResponse)ex.Response;
                  if (resp01.StatusCode == HttpStatusCode.NotFound)
                  {
                      vResult = false;
                  }
                  else
                     {
                         vResult = vResErrorDefault;
                     }
                 }
                 else
                     {
                         vResult = vResErrorDefault;
                     }
                 }
           finally
           {
               // Don't forget to close your response.
               if (response != null)
               {
                   response.Close();
               }
           }
           return vResult;
}

Answer 10

定义超时的Anoter版本：

public bool URLExists(string url,int timeout = 5000)
{
    ...
    webRequest.Timeout = timeout; // miliseconds
    ...
}

Answer 11

这对我有用：

bool HaveFile(string url)
        {
            try
            {
                using (WebClient webClient = new WebClient())
                {
                    webClient.DownloadString(url);
                }
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

我可以检查URL上是否存在文件？

11 个答案: