User753101303 posted
Hi,
We would need some context (ie you do have a full posback or are you using an update panel ? you could consider also to do the Ajax call yourself) as well as the business goal (which purpose does it serve rather than just that you have
to use a "client callback").
For now there is nothing telling that this is not a full postback in which case you could likely just alter the page the way you want or if really needed to register which JavaScript code should run when the page loads...
Or if you are using an UpdatePanel for example please tell us so.