Call Javascript from code behind function in asp.net

How to Call Javascript function from code behind after button click event;

 string popupScript = "<script language='javascript'>" +
                         "alert('hai');" +
                       "</script>";

                ClientScript.RegisterStartupScript(Page.GetType(), "script", popupScript开发者_JS百科, true);

I tried above script but not working

You already added the script tags, so pass false as last argument:

string popupScript = 
    "<script type=\"text/javascript\">" +
    "alert('hai');" +
    "</script>";
ClientScript.RegisterStartupScript(Page.GetType(), "script", popupScript, false);

or leave it to the framework:

string popupScript = "alert('hai');";
ClientScript.RegisterStartupScript(Page.GetType(), "script", popupScript, true);

Since ClientScript.RegisterStartupScript is an overloaded function you can also leave it without the last 'addScriptTags' boolean when you want to put in the script tags yourself. It defaults to false.

Remove the language attribute. Change it to type='text/javascript'

In addition to all of the advice of the others, if the element firing this event is in an update panel you will need a full post-back trigger.