title: Should I disable WebClient caching?
body: <p>WebClient.DownloadStringAsync does cache the server response.
  After once getting a response from the server I get a response even without internet connection!</p>
  
  <p>Is WebClient caching smart enough to determine from the server response how long to cache?
  Or is it buggy and I should disable caching.</p>
  
  <p>Backgound info:</p>
  
  <p>Url: <a href="http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml" rel="nofollow">http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml</a></p>
  
  <p>Fiddler trace:</p>
  
  <p>GET /stats/eurofxref/eurofxref-daily.xml HTTP/1.1
  Accept: <em>/</em>
  Referer: file:///Applications/Install/4D0DF1F7-1481-45CA-86BE-C14FF5CCD955/Install/
  Accept-Encoding: identity
  User-Agent: NativeHost
  Host: www.ecb.europa.eu
  Connection: Keep-Alive</p>
  
  <p>HTTP/1.1 200 OK
  Date: Sun, 25 Mar 2012 08:54:40 GMT
  Server: Apache/2.2.3 (Linux/SUSE)
  Last-Modified: Fri, 23 Mar 2012 13:31:39 GMT
  ETag: "19d4e5-6a9-4bbe90b5904c0"
  Accept-Ranges: bytes
  Content-Length: 1705
  Keep-Alive: timeout=3, max=200
  Connection: Keep-Alive
  Content-Type: text/xml
  Set-Cookie: BIGipServerPOOL.www.ecb.europa.eu_HTTP=2684883628.16415.0000; path=/
  
  ...</p>
  
  <p>Disabling caching via Headers does not work:</p>
  
  <p>.Headers("cache-control") = "no-cache" 
  .Headers("HttpRequestHeader.IfModifiedSince") = DateTime.UtcNow.ToString()</p>
  
  <p>Disabling caching via appending uniqa parameter works:</p>
  
  <p>"http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml" &amp; "?MakeRequestUnique=" &amp; Environment.TickCount</p>