ASP.NET C# 响应。写入不显示消息

Question

So I am told just by using Javascript inside the Response.Write method, I can display an alert/message box on ASP.NET C#.

Using Response.Write("<script>alert('Data inserted successfully')</script>") as the template given in other answers.

When I first attempted to use it, it worked, displaying the message and redirecting me sucessfully. Since then, it has not worked, I only changed the message to display and also where the redirect URL would go after. Logically it is working as it is taking me back to the application form, it just isn't displaying the message.

Can anyone explain why it suddenly doesn't work?

Code;

        public ActionResult UpdateApplication(int ApplicationId, ApplicationEdit applicationEdit)
    {
        if(applicationEdit.Firm == false)
        try
        {
            applicationService.UpdateApplication(applicationEdit, ApplicationId);
            return RedirectToAction("GetUser", "User", new { ApplicationId = applicationEdit.ApplicationId });
        }
        catch
        {
            return View();
        }
        else
        {
            Response.Write("<script language=javascript>alert('Sorry, You can only have 1 firm application to send off, please update the old application and untick firm option on other application first.')</script>");
            return RedirectToAction("UpdateApplication", new { ApplicationId = applicationEdit.ApplicationId });
        }
    }

Answer 1

Because you're redirecting the user:

return RedirectToAction("UpdateApplication", new { ApplicationId = applicationEdit.ApplicationId });

This returns a redirect HTTP code to the browser (HTTP 307 or 308 I imagine) which tells the browser to direct the user to the specified URL. Since the browser knows it's redirecting the user, it has no reason to render any content in the response.

Either return content to be rendered in the browser or return a redirect response, but not both. If you return the view instead then you should see your <script> element in the resulting response. If you want to redirect then any message you want to display to the user should be on that next page, not in the current response.

---

As an aside, using Response.Write in an ASP.NET MVC application is pretty much always the wrong approach. Any client-side code should be in or referenced by the view, and you can use data on the view's model to conditionally render or not render that content.