how do i call javascript function at the end of button click in asp.net
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I tried


    Protected Sub btn_add_question_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_add_question.Click
            frm_course.Visible = False
            question_div.Visible = True
            ScriptManager.RegisterClientScriptBlock(btn_add_question, Me.GetType(), "BlockName", "alert('hello world');", True)
        End Sub

and 

    Protected Sub btn_add_question_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_add_question.Click
            frm_course.Visible = False
            question_div.Visible = True
            Page.ClientScript.RegisterStartupScript(Me.GetType, "Javascript", "alert('hello')")
        End Sub

But, alert message is not showing. Need Help !!