MVC 弹出提示框

第一种弹框成功后要刷新界面 

[HttpPost]   
        public ActionResult Add(Maticsoft.Model.Project.ProjectMoneyPlan model)   
        {   
            model.Money = new Maticsoft.Model.Struct.DRMB(model.Money).ToDouble().ToString();   
            Maticsoft.BLL.User.LoginUser login = new Maticsoft.BLL.User.LoginUser();   
            model.Creater = login.Email;   
            try  
            {   
                if (bll.Exist("Pro_MoneyPlan", "where ProCode='" + model.ProCode + "' ", "ProCode") && bll.Exist("Pro_MoneyPlan", "where Year=" + model.Year , "Year") && bll.Exist("Pro_MoneyPlan", "where Month=" + model.Month, "Month"))   
                {   
                    ///弹框   
                   string script = String.Format("<script>alert('数据已经存在！');location.href='{0}'</script>",  Url.Action("Add"));      
                   return Content(script ,"Text/html");                  
                }   
                else  
                {   
                    bll.Add(model);   
                    return View("List");   
                }   
            }   
            catch (Exception ex)   
            {   
                return new Maticsoft.BLL.Error().DoError(ex);   
            }   
        }   

第二种弹框成功后不刷新界面：

[HttpPost]   
        public ActionResult Add(Maticsoft.Model.Project.ProjectMoneyPlan model)   
        {   
            model.Money = new Maticsoft.Model.Struct.DRMB(model.Money).ToDouble().ToString();   
            Maticsoft.BLL.User.LoginUser login = new Maticsoft.BLL.User.LoginUser();   
            model.Creater = login.Email;   
            try  
            {   
                if (bll.Exist("Pro_MoneyPlan", "where ProCode='" + model.ProCode + "' ", "ProCode") && bll.Exist("Pro_MoneyPlan", "where Year=" + model.Year , "Year") && bll.Exist("Pro_MoneyPlan", "where Month=" + model.Month, "Month"))   
                {   
                   ViewData["ProName"] = SelecOpption.GetOpption("PRO_B", "", "Code,Name");//获取项目名称   
                   ViewData["Year"] = GetYear();   
                   ViewData["Month"] = GetMonth();   
                   ///弹框   
                   ViewBag.isExist = false;   
                   return View();   
                }   
                else  
                {   
                    bll.Add(model);   
                    return View("List");   
                }   
            }   
            catch (Exception ex)   
            {   
                return new Maticsoft.BLL.Error().DoError(ex);   
            }   
        }   

前台：

@if (ViewBag.isExist == false)   
{   
    <script type="text/javascript">   
        alert("您要添加的数据已经存在！")   
    </script>   
}