Display error message on the view from controller asp.net mvc 5

Question

I am new to web development and trying to learn ASP.Net MVC 5. I am looking for one record in database if the record is not found then I want to display an error message to the user. Below is my attempt:

Controller

    [HttpGet]     public ActionResult Search()     {         return View();     }      [HttpPost]     [ValidateAntiForgeryToken]     public ActionResult Search(ForgotPasswordMV viewModel)     {         if (Temp.Check(viewModel.Email))             return RedirectToAction("VerifyToken", new { query = viewModel.Email });         else         {             ViewBag.ErrorMessage = "Email not found or matched";             return View();         }     } 

View:

<p>@ViewBag.ErrorMessage</p> 

ViewModel

public class ForgotPasswordMV {     [Display(Name = "Enter your email"), Required]     public string Email { get; set; } } 

But I read somewhere that I should put one property in my view model and set the error message on that property. I am confused now, how to achieve that and how to display the error in View then? And which one is the recommended/best practice?

Answer 1

But I read somewhere that I should put one property in my view model and set the error message on that property. I am confused now, how to achieve that and how to display the error in View then? And which one is the recommended/best practice?

The best practice is to alter the ModelState dictionary property of your controller like this:

[HttpPost] [ValidateAntiForgeryToken] public ActionResult Search(ForgotPasswordMV viewModel) {     // ...      else     {         ModelState.AddModelError(nameof(ForgotPasswordMV.Email), "Email not found or matched");         return View(viewModel);     } } 

Then in your view add the line below next to your email field;

@Html.ValidationMessageFor(m => m.Email) 

Answer 2

But I read somewhere that I should put one property in my view model and set the error message on that property.

That's correct. You could add the error message to your view model:

public class ForgotPasswordMV {     [Display(Name = "Enter your email"), Required]     public string Email { get; set; }      public string ErrorMessage { get; set; } } 

and then set this property on your view model and pass the view model to the view:

... else {     viewModel.ErrorMessage = "Email not found or matched";     return View(viewModel); } 

and finally in your strongly typed view use the property on your model:

@model ForgotPasswordMV ... <p>@Model.ErrorMessage</p> 

So basically here we are replacing the use of ViewBag with a strongly typed view model.