asp.net后台弹出提示框

Response.Write("");
    //第三种
    ClientScriptManager scriptManager = ((Page)System.Web.HttpContext.Current.Handler).ClientScript;
    scriptManager.RegisterStartupScript(typeof(string), "", "alert('第三种弹出框');", true);
    //第四种
    Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "");