HttpWebRequest.IfModifiedSince Property

    // Create a new 'Uri' object with the mentioned string.
    Uri myUri =new Uri("http://www.contoso.com");			
    // Create a new 'HttpWebRequest' object with the above 'Uri' object.
    HttpWebRequest myHttpWebRequest= (HttpWebRequest)WebRequest.Create(myUri);

    // Create a new 'DateTime' object.
    DateTime targetDate = DateTime.Now;
    // Set a target date of a week ago
    targetDate.AddDays(-7.0);
    myHttpWebRequest.IfModifiedSince = targetDate;

    try   
    {
      // Assign the response object of 'HttpWebRequest' to a 'HttpWebResponse' variable.
      HttpWebResponse myHttpWebResponse=(HttpWebResponse)myHttpWebRequest.GetResponse();
      Console.WriteLine("Response headers for recently modified page\n{0}\n",myHttpWebResponse.Headers);
      Stream streamResponse=myHttpWebResponse.GetResponseStream();
      StreamReader streamRead = new StreamReader( streamResponse );
      Char[] readBuff = new Char[256];
      int count = streamRead.Read( readBuff, 0, 256 );
      Console.WriteLine("\nThe contents of Html Page are :  \n");	

      while (count > 0) 
      {
        String outputData = new String(readBuff, 0, count);
        Console.Write(outputData);
        count = streamRead.Read(readBuff, 0, 256);
      }
      // Close the Stream object.
      streamResponse.Close();
      streamRead.Close();
      // Release the HttpWebResponse Resource.
      myHttpWebResponse.Close();
				
      Console.WriteLine("\nPress 'Enter' key to continue.................");	
      Console.Read();
    }
    catch(WebException e)
    {
      if (e.Response != null)
      {
        if ( ((HttpWebResponse)e.Response).StatusCode == HttpStatusCode.NotModified)
          Console.WriteLine("\nThe page has not been modified since "+targetDate);
        else
          Console.WriteLine("\nUnexpected status code = " + ((HttpWebResponse)e.Response).StatusCode);  
      }
      else
        Console.WriteLine("\nUnexpected Web Exception " + e.Message); 
    }

// Create a new 'Uri' object with the mentioned string.
Uri* myUri = new Uri(S"http://www.contoso.com");
// Create a new 'HttpWebRequest' object with the above 'Uri' object.
HttpWebRequest* myHttpWebRequest =
   dynamic_cast<HttpWebRequest*>(WebRequest::Create(myUri));
// Create a new 'DateTime' object.
DateTime today = DateTime::Now;
if (DateTime::Compare(today, myHttpWebRequest->IfModifiedSince)==0) {
   // Assign the response object of 'HttpWebRequest' to a 'HttpWebResponse' variable.
   HttpWebResponse* myHttpWebResponse =
      dynamic_cast<HttpWebResponse*>(myHttpWebRequest->GetResponse());
   Console::WriteLine(S"Response headers \n {0}\n",
      myHttpWebResponse->Headers);
   Stream* streamResponse = myHttpWebResponse->GetResponseStream();
   StreamReader* streamRead = new StreamReader(streamResponse);
   Char readBuff[] = new Char[256];
   int count = streamRead->Read(readBuff, 0, 256);
   Console::WriteLine(S"\nThe contents of Html Page are :  \n");
   while (count > 0) {
      String* outputData = new String(readBuff, 0, count);
      Console::Write(outputData);
      count = streamRead->Read(readBuff, 0, 256);
   }
   // Close the Stream object.
   streamResponse->Close();
   streamRead->Close();
   // Release the HttpWebResponse Resource.
   myHttpWebResponse->Close();
   Console::WriteLine(S"\nPress 'Enter' key to continue.................");
   Console::Read();
} else {
   Console::WriteLine(S"\nThe page has been modified since {0}", __box( today));
}