How to change the default error message of built-in ValidationAttributes?

Question

I would like to replace the default error message for for example RequiredAttribute or RegularExpressionAttribute with my own messages, so that I wouldn't need to specify the explicit ErrorMessage at attribute usage.

EDIT: Last part of the sentence means that I'm aware of the ability to specify my own ErrorMessage at attribute usage, and I would like to avoid it for keeping the project DRY.

Is it possible somehow? I haven't found any related property in the .NET library, and I currently have no idea how I could replace the .NET resources where the default messages are stored.

Why exactly do you need another way when you can pass your **own** error message with RequiredAttribute? — Sunny Sharma, May 01 '15 at 13:23
Because I would like a common message which I'm using in most cases. Now I need to repeat it at every usage of the attribute. — Zoltán Tamási, May 01 '15 at 13:24
Cool, better you create a custom attribute! See Richard's answer! — Sunny Sharma, May 01 '15 at 13:40

score 1 · Accepted Answer · edited May 23 '17 at 12:14

1

Just create your own version of the [Required] attribute that has a default message that you want. If you only want to use a custom error message have it inherit from RequiredAttribute so you can take advantage of the same IsValid logic

public class MyRequired : RequiredAttribute
{
    public MyRequired()
    {
        this.ErrorMessage = "Custom Validation Error Message.";
    }
}

If you need even finer control over other validation behaviors, you can create your own DataAnnotation Attributes.

public class MyRequired : ValidationAttribute
{
    public MyRequired() : base("My Custom Message")
    {

    }

    public override bool IsValid(object value)
    {
        //Your custom validation logic
        return (value != null);
    }
}

edited May 23 '17 at 12:14

Community

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1

answered May 01 '15 at 13:24

ryanyuyu

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Thanks, I knew about this way but I hoped for a nicer one. Anyway why not just not override the IsValid function? – Zoltán Tamási May 01 '15 at 13:43
? `IsValid` is being overridden. I don't understand what you're saying. – ryanyuyu May 01 '15 at 13:46
It's easier to override the relevant attribute (e.g. RequiredAttribute) rather than ValidationAttribute where you also need to implement `IsValid` again. – Richard May 01 '15 at 13:49
Ah, I didn't notice that you've inherited from ValidationAttribute, I thought you've inherited from RequiredAttribute and that's why I questioned why you've overridden the IsValid method. Sorry for the not too correct english sentence too :) – Zoltán Tamási May 01 '15 at 13:51
Ok yes I see what you mean, give me a few minutes to update. This will currently work, but your suggestions are another improvement. – ryanyuyu May 01 '15 at 13:52
@Richard thanks for the extra advice. Updated answer. – ryanyuyu May 01 '15 at 14:03

How to change the default error message of built-in ValidationAttributes?

1 Answers1