Why, what's wrong with OnChange event? Wouldn't OnKeyUp react also to arrow keys and similar, causing unnecessary queries to the database?
Exactly because of that. You can filter "illegal" keys.
the OnChange-Event doesn't ship the Key being pressed.
Now imagine having a "Search-History" (stored in a List or whatever).
And now imagine pressing the Arrow-Down-Button to quickswitch to the searchphrase before your current one.....
EDIT: And just looking at his First Post, i'm going to throw a Spanner into the gearbox, and enter a "%" as the first Character using his code....
EDIT2: btw: Or i'd use OnKeyDown in that case....