check if file exist in the same URL but not in local server

Question

I want to check if a file exists in the same URL but not on the server. What I meant was, say if I have a domain https://example.com/ and a folder in the domain https://example.com**/s3files/** automatically points or redirect to S3 so that https://example.com/**s3files/test.png**, downloads a file from s3 directly.

How can I test in my controller that said file exists?

I'm trying to do something like this

 fileName = $"/s3files/{fileName}";
 if (!File.Exists(path))
    return "/assets/images/no-image.png";

 return fileName;

But I'm not sure if It's correct since File.Exist checks the local directory of the server if the file exists in the '/s3files' subdirectory.

Since my controller doesn't know about the routing part and its current domain URL, how can I check if the file exists?

Answer 1

Maybe this will help...

public static bool checkIfFileExists(string url)
        {
            bool found = false;
 
            var request = WebRequest.Create(url);
            request.Method = "HEAD";
            request.Timeout = 30;
 
            HttpWebResponse response = null;
 
            try
            {
                response = (HttpWebResponse)request.GetResponse();
                found = true;
            }
            catch (WebException webException)
            {
            }
            finally
            {
                if (response != null)
                {
                    response.Close();
                }
            }
 
            return found;
        }

Answer 2

you can send a HEAD request, it will check the metadata of the file without actually downloading it.

Here is the code for you.

using (var client = new HttpClient())
{
    var fileUrl = $"https://example.com/s3files/{fileName}";
    var response = await client.SendAsync(new HttpRequestMessage(HttpMethod.Head, fileUrl));

    if (response.StatusCode == HttpStatusCode.OK)
    {
        // File exists
        return fileUrl;
    }
    else
    {
        // File doesn't exist
        return "/assets/images/no-image.png";
    }
}

It will return the status code 200 if the file is present else it will return 404.