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?

Answer 1

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.

Answer 2

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.

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).