Saving images from the web with GetResponseStream()

[Mattias]

I'm saving pictures on my harddrive from our webcam with GetResponseStream()
.. Everything works fine, but after approximately 1h identical images are
being saved. I checked the webpage but those pictures are still being
refreshed.

Code snippet:
req = (System.Net.HttpWebRequest) System.Net.WebRequest.Create(fullpath);
req.Credentials = System.Net.CredentialCache.DefaultCredentials;
// Return request in a response stream
res = (System.Net.HttpWebResponse) req.GetResponse();
System.IO.Stream str = res.GetResponseStream();
if(str!=null)
{
Image img = Image.FromStream(str);
img.Save(fileName, System.Drawing.Imaging.ImageFormat.Jpeg);
}