I have found two answers to this question:
Response.Buffer = True
Response.ExpiresAbsolute = Now().Subtract(New TimeSpan(1, 0, 0, 0))
Response.Expires = 0
Response.CacheControl = "no-cache"
Note that Response.Expires is deprecated in ASP.NET and Response.Cache.SetExpires should be used instead.
<%@ OutputCache location="none" %>
More details at http://www.c-sharpcorner.com/asp/Articles/CachingInASPDPL.asp