`[AllowedValues]` and `[DeniedValues]` case insensitivness suport

[BachiMjavanadze]

I think it would be better if the [AllowedValues] and [Denied Values] attributes had support for case insensitivity. So instead:

[AllowedValues("bad", "Bad", "bAd", "baD", "BAD")]

or defining custom attribute, possible to write this:

[AllowedValues("bad" CaseInsensitive = true)]

[ghost]

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Issue Details

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I think it would be better if the `[AllowedValues]` and `[Denied Values]` attributes had support for case insensitivity. So instead: `[AllowedValues("bad", "Bad", "bAd", "baD", "BAD")]` or defining custom attribute, possible to write this: `[AllowedValues("bad" CaseInsensitive = true)]`

Author:	BachiMjavanadze
Assignees:	-
Labels:	`area-System.ComponentModel.DataAnnotations`, `untriaged`
Milestone:	-

[eiriktsarpalis]

The attributes work on arbitrary values, not just strings. A general-purpose API would necessitate passing an IEqualityComparer parameter, however that typically doesn't work with attribute annotations -- you would need to manually define one via inheritance.

[BachiMjavanadze]

Ok!