Downloading PDF content from a website -

I'm trying to download a PDF to my desktop - The PDF upda开发者_如何学Pythontes about every couple days with new content, and I was trying to see if there is a way to have the PDF automatically update its self when it has fresh content without having to go to the actual link.

-- http://www.uakron.edu/dotAsset/1265971.pdf

Assuming this is even remotely a programming question, you could try a HTTP HEAD query (ideally sending a If-Modified-Since header in your request), and inspect the response headers - if the server is friendly, it'll tell you whether it hasn't been updated via a 304 response code.

If you don't get a 304, then issue a GET request and save the response stream.

You could also just try issuing a GET with last-modified (skipping the HEAD); but a HEAD request might save some bandwidth if the server isn't entirely happy with just a GET / 304.

Not tested extensively, but:

using System;
using System.IO;
using System.Net;

static class Program
{
    static void Main()
    {
        string url = "http://www.uakron.edu/dotAsset/1265971.pdf", localPath = "1265971.pdf";

        var req = (HttpWebRequest)WebRequest.Create(url);
        req.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip;
        req.Headers.Add("Accept-Encoding","gzip,deflate");
        if(File.Exists(localPath))
            req.IfModifiedSince = File.GetLastWriteTimeUtc(localPath);
        try
        {
            using (var resp = req.GetResponse())
            {
                int len;
                checked
                {
                    len = (int)resp.ContentLength;
                }
                using (var file = File.Create(localPath))
                using (var data = resp.GetResponseStream())
                {
                    byte[] buffer = new byte[4 * 1024];
                    int bytesRead;
                    while (len > 0 && (bytesRead = data.Read(buffer, 0, Math.Min(len, buffer.Length))) > 0)
                    {
                        len -= bytesRead;
                        file.Write(buffer, 0, bytesRead);
                    }
                }
            }
            Console.WriteLine("New version downloaded");
        }
        catch (WebException ex)
        {
            if (ex.Response == null || ex.Status != WebExceptionStatus.ProtocolError)
                throw;
            Console.WriteLine("Not updated");
        }
    }
}