Does a web file exist - using same function to get the Content Type

Question

I have a function that is coded to get the Content-Type of a web file.

Here is the function:

public string GetContentTypeOfUri(string uri)
{
    try
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
        request.Method = "HEAD";
        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {
            var contentType = response.Headers["Content-Type"];
            return (contentType);
        }
    }
    catch (Exception ex)
    {
        return "error";
    }
}

Rather than writing a whole different function to detect if a web file exists, how can I calculate if a file exists from the same code as used to get the Content-Type ?

If I use a uri of a file that does not exist, an exception occurs. The ex.HResult equals -2146233079 when this exception occurs, with a message = "The remote name could not be resolved: '[address name]'".

Is it safe to say that when an exception occurs, and the ex.HResult equals -2146233079, the file does not exist?

Is there an easier/better way to work this out?

Thanks in advance

EDIT

Here is the HttpClient code that I have:

public async Task<string> GetContentTypeAsync(string uri)
{
    using (var httpClient = new HttpClient())
    {
        var request = new HttpRequestMessage(HttpMethod.Post, uri);
        request.Method = new HttpMethod("HEAD");
        var response = await httpClient.SendAsync(request);
        string contentType = response.Content.Headers.ContentType.ToString();
        return contentType;
    }
}

Your example web address does inform me that the address does not exist, however, if I have a web address that does not exist such as http://www.usa.canon.com/app/html/HDV/HG10/images/hg10_sample_image_03.jpg5 , I am getting a StatusCode of OK, as a Text content type is returned as a custom error page.

Answer 1

There are two possible "not exists" scenarios. It sounds like you've identified one of them - when the server name in the URL is incorrect and so the request cannot even be sent.

But you're not accounting for the other error - that you can reach a remote server but it denies all knowledge of a specific file. For that scenario, you ought to be checking for status 404 on the response .

For cleaner handling of your current scenario (server doesn't exist) you could use the Uri class to extract the Host name from the uri string and perform a manual DNS lookup - which would allow you to code for this likely scenario without having to catch exceptions - which is generally frowned upon when its an expected scenario.