If-Modified-Since HTTP Header

Demonstrates how to use the if-modified-since header in VB.NET to send an HTTP request that will only return the full page if it has been modified. NOTE: This depends on the HTTP server supporting if-modified-since, and dynamic pages may never return a 304 status code.

        Dim http As New Chilkat.Http
        http.UnlockComponent("anything for 30-day trial")

        ' Return the HTML page only if it's been modified since this date...
        http.SetRequestHeader("If-Modified-Since", "Thu, 07 Sep 2006 17:12:50 GMT")

        Dim html As String
        html = http.QuickGetStr("http://www.thaibugs.com/")
        If (Len(html) = 0) Then
            If (http.LastStatus = 304) Then
                MessageBox.Show("Has not been modified!")
            Else
                MessageBox.Show(http.LastStatus)
                MessageBox.Show(http.LastResponseHeader)
            End If
        Else
            MessageBox.Show(http.LastResponseHeader)
        End If