Javascript Alert message in c# asp.net (for testing purpose only)

protected void Button1_Click(object sender, EventArgs e)

    {

        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record Inserted Successfully')", true);

            }

or if above function not work, use below code:-

ScriptManager.RegisterStartupScript(this, this.GetType(), "msg", "alert('Excess Student uploaded according to max batch size.....');", true);