How to prevent client Cache? I want every client request get sent to the server even if it’s behind a proxy server and for any browser setting.

You can use tag

<%@ OutputCache Duration='0' Location='None' VaryByParam='none' %> 

or

VB.NET

Response.Cache.SetCacheability(HttpCacheability.NoCache)

C#

Response.Cache.SetCacheability(HttpCacheability.NoCache);