How to override default required error message

Question

I have an old C# MVC 2.0 web application.

Whenever I use a [Required] attribute, the default validation error message goes:

The [whatever] field is required.

My problem is that the application isn't in English, so I basically have to change the attribute call to [Required(ErrorMessage = "Le champ [whatever] est requis.")] everywhere.

Is there a way to override the default error message so I only have to specify it when I want a specific message?

I'm looking for something like:

DefaultRequiredMessage = "Le champ {0} est requis.";

I didn't get, what's your problem with `[Required(ErrorMessage = "MyNotEnglishMessage")]`? — Salah Akbari, Oct 29 '18 at 09:14
I don't want to have to write the same message everywhere in my app, I'd like to follow the DRY principle — Rafalon, Oct 29 '18 at 09:15
Could you not just install the French language pack and set CurrentUICulture to a French culture (e.g. fr or fr-FR)? Or if you don't want to install a language pack, use a custom resource manager: https://stackoverflow.com/questions/2347650/how-to-use-dataannotations-errormessageresourcename-with-custom-resource-solutio — Joe, Oct 29 '18 at 09:43
@Joe this is a very old app, so I don't even know if I could find the French language pack, and I don't really want to take a risk to mess up everything if it doesn't exactly match the one needed. I think S.Akbari's solution is close to your second option, so I'd rather see if this works as expected as it has little chances to mess up things. However, I agree that having a French language pack would be a great solution! — Rafalon, Oct 29 '18 at 09:57

Salah Akbari · Accepted Answer · 2018-10-29T13:22:00.273

8

You can create a class and inherit it from RequiredAttribute. Something like this:

public class CustomRequired: RequiredAttribute
{
    public CustomRequired()
    {
        this.ErrorMessage = "Le champ est requis.";
    }
}

Or:

public class CustomRequired: RequiredAttribute
{
    public override string FormatErrorMessage(string whatever)
    {
        return !String.IsNullOrEmpty(ErrorMessage)
            ? ErrorMessage
            : $"Le champ {whatever} est requis.";
    }
}

You should use CustomRequired with your properties, rather than [Required].

edited Oct 29 '18 at 13:22

answered Oct 29 '18 at 09:21

Salah Akbari

39,330
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How would you change it to include the field name in the error message? – Rafalon Oct 29 '18 at 09:23
1

Shouldn't it be `CustomRequiredAttribute` instead of `CustomRequired`? Anyway thank you for this, let me just try it and if it works as expected I'll accept this answer – Rafalon Oct 29 '18 at 09:31
@Rafalon It is just the name of your custom class. Feel free to name it to whatever you like :) – Salah Akbari Oct 29 '18 at 09:32
1

Yeah, I just thought it should end with `Attribute` so we can use `[CustomRequired]` – Rafalon Oct 29 '18 at 09:33

score 1 · Answer 2 · edited Dec 16 '19 at 12:57

Please perform the below operation to override default required error message:

Create a custom adapter inheriting the RequiredAttributeAdapter as below :

public class YourRequiredAttributeAdapter : DataAnnotationsModelValidator<RequiredAttribute>
{
    public YourRequiredAttributeAdapter(ModelMetadata metadata, ControllerContext context, RequiredAttribute attribute)
        : base(metadata, context, attribute)
    {
        if (string.IsNullOrWhiteSpace(attribute.ErrorMessage)
            )
        {
            attribute.ErrorMessageResourceType ="Your resource file";
            attribute.ErrorMessageResourceName = "Keep the key name in resource file as "PropertyValueRequired";
        }
    }

}

Register the Adapter in Global.asax Application_Start() as below:

DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(RequiredAttribute), typeof(YourRequiredAttributeAdapter));

Resource File Configuration:

How to override default required error message

2 Answers2

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