c#: Why Validator omitts a ValidationAttribute validation if multiple ValidationAttribute are present?

Question

I have a simple WPF-Application and I use the System.ComponentModel.DataAnnotations.Validator to validate data.

I've created a custom ValidationAttribute which I can set multiple times on a member (AllowMultiple=True).

Simplified something like that:

public class SampleClass
{
    [CustomValidationAttribute("para bla bla")] // as first
    [CustomValidationAttribute("para blu blu")] // as second
    public string MemberA { get; set; }
}

When I now perform Validator.TryValidate(..., true) only the second attribute ("blu blu") is validated, the first, in a magical way, is omitted.

Do I miss something? Or is this a feature? If so, who can I get rid of it?

Thank you for your ideas.

[EDIT 2019-03-12 17:10 CET]

Even when I add an attribute extra, only the validation of the the last one is executed.

public class SampleClass
{
    [CustomValidationAttribute("para bla bla")] // as first
    [CustomValidationAttribute("para blu blu")] // as second
    [CustomValidationAttribute("para bibi")] // as thrid
    public string MemberA { get; set; }
}

"Bibi" is validated, the others not ... Strange, isn't it?

Maybe the first one is overloaded with the second custom validator? — Gabriel Costin
– Gabriel Costin, Commented Mar 11, 2019 at 15:24
@GabrielCostin Not sure if I understand you correctly: You assume, the first attribute is replaced with the second one? — user1470240
– user1470240, Commented Mar 12, 2019 at 16:05
Yes that's what I am assuming, in fact you can try with another attribute, for exemple StringLength , define 2 or more attributes and check the output — Gabriel Costin
– Gabriel Costin, Commented Mar 13, 2019 at 7:25
Confirmed: The behavior is, that only the last declared validation attribute each type is used for validation. This knowledge is nice, but back to topic: How can I change that behavior? I find it very strange, that same-type-attributes are just swallowed, up instead an aproppriate exception is thrown ... — user1470240
– user1470240, Commented Mar 13, 2019 at 12:42
Well I am not that experienced to offer you a very good solution , what I would do is just like create that CustomValidationAttribute and maybe instead of having a string as parameter type I would go for an array of strings or whatever — Gabriel Costin
– Gabriel Costin, Commented Mar 13, 2019 at 14:16

Terrence · Accepted Answer · 2024-08-22 18:01:00Z

0

Per Custom validation attribute with multiple instances problem, this can be resolved by uniquely identifying each instance with an override of TypeId:

public override object TypeId { get; } = new();

answered Aug 22, 2024 at 18:01

Terrence

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1 Comment

user1470240 Over a year ago

Thanks - that's the solution. If I got some time, I will check if out-of-the-box attributes, which uses allowmultipe=true. also use this technique =)

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