can I check if a file exists at a URL?

Question

I know I can locally, on my filesystem, check if a file exists:

if(File.Exists(path))

Can I check at a particular remote URL?

See also here for mixing WebClient and HEAD in a single answer: stackoverflow.com/questions/153451#156750 — Marc Gravell
– Marc Gravell, Commented Dec 30, 2009 at 13:26
Marc, why would using a custom class be better in this case? Later on you even suggest on using try / catch. — cregox
– cregox, Commented Aug 17, 2012 at 21:00

Ravenix · Accepted Answer · 2016-08-12 12:02:33Z

97

If you're attempting to verify the existence of a web resource, I would recommend using the HttpWebRequest class. This will allow you to send a HEAD request to the URL in question. Only the response headers will be returned, even if the resource exists.

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();
    }
}

Of course, if you want to download the resource if it exists it would most likely be more efficient to send a GET request instead (by not setting the Method property to "HEAD", or by using the WebClient class).

edited Aug 12, 2016 at 12:02

Ravenix

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answered Dec 30, 2009 at 12:40

Justin Rusbatch

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3 Comments

Kirk Woll Over a year ago

I'd recommend checking for a 404 rather than just any 'ol error code. If it's a 500, for example, then it might be that the "file" exists, but that the server encountered (a perhaps temporary) error when servicing the request. To check for 404s, make sure to cast ex.Response to HttpWebResponse, and then you can compare StatusCode to HttpStatusCode.NotFound.

Mmm Over a year ago

I'm surprised I'm the first one to note that response should be Disposed!

PRMan Over a year ago

If you use a using on response = (HttpWebResponse)request.GetResponse(); it will be disposed of automatically.

cregox · Accepted Answer · 2014-11-13 17:13:47Z

20

If you want to just copy & paste Justin's code and get a method to use, here's how I've implemented it:

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;
    }
}

I'll keep his observation:

If you want to download the resource, and it exists, it would be more efficient to send a GET request instead by not setting the Method property to "HEAD" or by using the WebClient class.

edited Nov 13, 2014 at 17:13

answered Aug 17, 2012 at 21:11

cregox

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4 Comments

MrDustpan Over a year ago

Don't forget to close the response.

cregox Over a year ago

You're right, @MrDustpan. But I wonder if we still need to close it since we never assigned it anywhere...

cassiodoroVicinetti Over a year ago

I disagree about closing the response, since when the object is disposed it is also closed (compare referencesource.microsoft.com/#System/net/System/Net/… ).

user160357 Over a year ago

wrapping the best answer into a method, it then becomes the better answer

Mack · Accepted Answer · 2015-03-05 11:18:11Z

12

Below is a simplified version of the code:

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;
}

edited Mar 5, 2015 at 11:18

Mack

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answered May 8, 2013 at 10:07

Kavit Trivedi

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Comments

Oded · Accepted Answer · 2009-12-30 12:21:43Z

4

If you are using a unc path or a mapped drive, this will work fine.

If you are using a web address (http, ftp etc) you are better off using WebClient - you will get a WebException if it doesn't exist.

answered Dec 30, 2009 at 12:21

Oded

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Comments

LastEnd · Accepted Answer · 2014-08-01 21:51:56Z

4

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;
    }

edited Aug 1, 2014 at 21:51

answered Aug 1, 2014 at 21:33

LastEnd

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1 Comment

LastEnd Over a year ago

Allows you to check webpage or any file located on a web server. Even if it tries to redirects to a 404 page.

Mofaggol Hoshen · Accepted Answer · 2020-06-05 15:44:41Z

4

I had the same problem to solve in asp.net core, I've solved with HttpClient

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;
            }
        }

answered Jun 5, 2020 at 15:44

Mofaggol Hoshen

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Comments

Andrew · Accepted Answer · 2019-09-17 10:59:26Z

2

My version:

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

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

        return true;
    }

edited Sep 17, 2019 at 10:59

answered Nov 13, 2016 at 7:17

Andrew

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Comments

nap · Accepted Answer · 2018-05-16 09:26:39Z

1

WebRequest will waiting long time(ignore the timeout user set) because not set proxy, so I change to use RestSharp to do this.

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

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

answered May 16, 2018 at 9:26

nap

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Comments

S. Kızıltoprak · Accepted Answer · 2020-10-08 13:29:48Z

Thanks for all answers. And I would like to add my implementation which includes default state when we get errors, for specific cases like mine.

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;
}

azouin · Accepted Answer · 2013-08-24 13:26:17Z

0

Anoter version with define timeout :

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

answered Aug 24, 2013 at 13:26

azouin

191 bronze badge

Comments

SilverStitch · Accepted Answer · 2021-06-03 15:20:15Z

0

This works for me:

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

edited Jun 3, 2021 at 15:20

answered Jun 3, 2021 at 15:13

SilverStitch

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