How can I implement custom error messages in ASP.NET MVC?

How can I implement custom error messages in ASP.NET MVC?

You can implement custom error messages in ASP.NET MVC by using the ModelState.AddModelError method in your controller.

Can you show me an example of how to use ModelState.AddModelError?

Sure! In your controller action, you can do something like this:

if (!ModelState.IsValid) {
    ModelState.AddModelError("FieldName", "Custom error message here.");
}

What if I want to display these error messages in my view?

You can display the error messages in your view using the Html.ValidationMessageFor helper method. For example:

@Html.ValidationMessageFor(model => model.FieldName)

Is there a way to customize the error message format?

Yes, you can customize the error message format by creating a custom validation attribute or by overriding the default error message in your model.