You can call the javascript function using register client script inside the onclick of the button.
ClientScript.RegisterStartupScript(Page.GetType, "Javascript",
"YourButton_OnClientClick_Handler();", true);
Question
Is it possible to fire the onclientclick after the onclick event for asp.net button? I am sending some values in session from onclick event and then I want to fire onclientclick. Any help would be advisable.
Solution
You can call the javascript function using register client script inside the onclick of the button.
ClientScript.RegisterStartupScript(Page.GetType, "Javascript",
"YourButton_OnClientClick_Handler();", true);
OTHER TIPS
Are you using an Update Panel? If yes, capture the endrequest and write code there..
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(endRequest);