Displaying all application errors in a view I'm learning ASP.NET Core with MVC pattern and I didn't find anything useful related to this argument. 

Actually I'm looking for a way to handle all the application errors inside a single View. The first thing that I did was create the View for display the error, this is the design (pretty simple though):

&lt;h2&gt;@(ViewBag.ErrorMessage == null ? "An error happened" : "" + @ViewBag.ErrorMessage + "")&lt;/h2&gt;


and this is the Error controller:

public class ErrorController : Controller
{
    [HttpGet]
    public IActionResult Index(string errorMessage)
    {
        ViewBag.ErrorMessage = errorMessage;
        return View();
    }
}


Essentially, I used the ViewBag for valorize a property called ErrorMessage which contains the parameter errorMessage.

Let me show an example of this logic for the email confirmation:

public async Task&lt;IActionResult&gt; ConfirmEmail(string userId, string token)
{
    if (userId == null || token == null)
    {
        return RedirectToAction("Index", "Error");
    }

    var user = await _userManager.FindByIdAsync(userId);

    if (user != null)
    {
       if (user.EmailConfirmed)
       { 
            return RedirectToAction("Index", "Error", new { errorMessage = "Email already confirmed" });
       }

       IdentityResult result;

       try
       {
           result = await _userManager.ConfirmEmailAsync(user, token);
       }
       catch (InvalidOperationException ex)
       {
           return RedirectToAction("Index", "Error", new { errorMessage = ex.Message });
       }

       if (result.Succeeded)
       {
           //TODO: Send another email
           return View("ConfirmEmail", user);
       }
    }

    return RedirectToAction("Index", "Error", new { errorMessage = "Utser not found" });
    }


Now, I'm not an expert yet of ASP.NET Core so I don't know if my practice is good enough for a production environment, someone could maybe propose a better way or improve my solution?
While I see no problem design-like or code-like, in the point of view of the user, It can be frustrating. 

I guess the method ConfirmEmail is called from a form. 

So, imagine how frustrating it is if you fill a form and if there is any error in this form, it redirects you to the Error View ?

Imo, Error display should be handled by Javascript/Html/Css on the same page which thrown the error to avoid losing any data from user's pov. Like, displaying a notification or even an error message below the field.

How you display the error should be specific of the error.