Comments by M I developer (Top 4 by date)

I havn't tested it on .Net 4.0 but it seems pretty logical that page event wont fire if Request validation occurs before the BeginRequest. so to make it work as your link recommended you should place <httpruntime requestvalidationmode="2.0"></httpruntime> in webconfig

Thanx

but in that case you have to check every input for malicious characters, i think that is over kill when Asp.Net validating those characters :)