can I check if a file exists at a URL?

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).

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.

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;
            }
        }

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;

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;
}

This works for me:

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