How to check if a file exists on a server using c# and the WebClient class

Question

In my application I use the WebClient class to download files from a Webserver by simply calling the DownloadFile method. Now I need to check whether a certain file exists prior to downloading it (or in case I just want to make sure that it exists). I've got two questions with that:

1. What is the best way to check whether a file exists on a server without transfering to much data across the wire? (It's quite a huge number of files I need to check)
2. Is there a way to get the size of a given remote file without downloading it?

Thanks in advance!

Answer 1

WebClient is fairly limited; if you switch to using WebRequest, then you gain the ability to send an HTTP HEAD request. When you issue the request, you should either get an error (if the file is missing), or a WebResponse with a valid ContentLength property.

Edit: Example code:

WebRequest request = WebRequest.Create(new Uri("http://www.example.com/"));
request.Method = "HEAD";

WebResponse response = request.GetResponse();
Console.WriteLine("{0} {1}", response.ContentLength, response.ContentType);

Answer 2

1) System.IO.File.Exists(Server.MapPath("../"));

2)ContentLegth property will help you to find the size of the file.

Answer 3

Here's a blog post I wrote regarding this matter in the past. I'm putting it here for future searches...