如何从控制器发送警报消息？

Question

将数据保存到数据库后，我试图从控制器发送成功或失败消息。 我知道这个问题可能会重复，但是我尝试了Internet上的每个选项，但对我来说都不起作用。 当我尝试这些答案时，有时没有错误出来，但输出也没有出来。.有时，当调试时，我发现“ 500（内部服务器错误）”。

我的代码在这里： 我的保存功能脚本：

 function Save() {
        var txtVal = $("#txtDescription").val();
        if (txtVal == "") {
            alert("Please Enter Description!");
        }
        else {
             var url = "/Master/SavetoDB";

                    $.ajax({
                        url: url,
                        data: {txtVal},
                        cache: false,
                        type: "GET",
  });
             $('input[type="text"]').val("");
            }
    }

我的控制器：

public ActionResult Category()
        {
            return View();
        }
public ActionResult SavetoDB(string txtVal)
        {
            DateTime tranDate = DateTime.Now;
            using (var db = new SWDataContext())
            {
                //try
                //{
                    IEnumerable<Category> _PCList = db.Category.AsNoTracking();
                    CategoryPRPC = db.Category.Where(a => a.Description.ToUpper() == txtVal.ToUpper()).FirstOrDefault();
                    if (!string.IsNullOrEmpty(txtVal))
                    {
                       if (PRPC != null)
                        {
                            if (PRPC.Description.ToUpper() == txtVal.ToUpper())
                            {
                            //return Content("-----");
                            ViewBag.Scripts = "<script>alert('Duplicate Record- Record already Exists!!!')</script>";
                            //TempData["AlertMessage"] = "Duplicate Record- Record already Exists!!!";
                            //ViewBag.Message = string.Format("Duplicate Record- Record already Exists!!!");
                            //ViewData["Success"] = "Duplicate Record- Record already Exists!!!";
                            //return new JavascriptResult { Script = "alert('Duplicate Record- Record already Exists!!!');" };
                            //return Content("<script language='javascript' type='text/javascript'>alert('Category saved Successfully!!!');</script>");
                            //throw new Exception("Duplicate Record- Record already Exists!!!");
                            //return Content("<script language='javascript' type='text/javascript'>alert('Duplicate Record- Record already Exists!!!');</script>");
                        }
                            //throw new Exception("Duplicate Record- Record already Exists!!!");
                            //return JavaScript(alert("Duplicate Record- Record already Exists!!!"));

                        }
                        else if (PRPC == null)
                        {
                            Category new_PRPC = new Category
                            {
                                Description = txtVal,
                                CreatedDate = tranDate,
                                CreatedUser="Admin",
                                 };
                            db.Category.Add(new_PRPC);
                            db.SaveChanges();
                        ViewBag.Scripts = "<script>alert('hello')</script>";
                        //TempData["AlertMessage"] = "Category saved Successfully!!!";
                        //ViewData["Success"] = "Category saved Successfully!!!'";
                        //return Content("<script language='javascript' type='text/javascript'>alert('Category saved Successfully!!!');</script>");

                    }

                    }
                //}
                //catch (Exception ex)
                //{
                //    return Json(new { success = "Fail", message = ex.Message }, JsonRequestBehavior.AllowGet);
                //}

                //return View("Category");
            }
            return View(ViewBag); /*Content("Data added successfully");*/
            //return View("Category");
            //return Json(new { result = result });
            //return new JavascriptResult { Script = "alert('Category saved Successfully!!!'');" };
            //return Content("<script language='javascript' type='text/javascript'>alert('Category saved Successfully!!!');</script>");
            //return Json(new { success = "success", message = "Data saved successfully" }, JsonRequestBehavior.AllowGet);
        }

我输入了所有从互联网答案中尝试过的注释代码。

看来，我什至尝试过

@if (ViewBag.SuccessMessage != null)
        {
            <text>
            <script>
                $(document).ready(function () {
                   alert('@ViewBag.SuccessMessage');
                });
            </script>
            </text>
        }

使用此命令时，出现500内部服务器错误。如何解决此问题。请帮助。