Decouple HtmlHelper.GetValidationAttributes from UnobtrusiveValidationAttributesGenerator.GetValidationAttributes

[roryprimrose]

MVC should not be tightly coupled to Microsoft's implementation of unobtrusive validation. For example, I want to use bootstrapValidator because it is a much better validation framework for working with bootstrap. As it stands, HtmlHelper is tightly coupled to UnobtrusiveValidationAttributesGenerator such that a different implementation cannot be used. This locks everyone into using unobtrusive validation rather than allowing support for custom validation attribute rendering on form fields.

[dougbu]

@roryprimrose the general HTML helper extensibility point is the overall IHtmlHelper / IHtmlHelper<TModel> implementations placed in DI. You're free to subclass HtmlHelper / HtmlHelper<TModel> or replace the default implementations with something entirely new.

For this particular coupling, I'd normally recommend overriding protected IDictionary<string, object> GetValidationAttributes(string name, ModelMetadata metadata). If we made that method virtual, would we solve your issue?

[Eilon]

@DamianEdwards I think you were toying with some ideas around validation extensibility - were you?

[roryprimrose]

It would certainly help. Presumably most of that method is still valid however. The only line that would require overriding is

return UnobtrusiveValidationAttributesGenerator.GetValidationAttributes(clientRules);

[yishaigalatzer]

@DamianEdwards / @dougbu - Could you get together and come up with an update for this design.

[dougbu]

👌

[dougbu]

Will generalize this ask a little bit and make a couple of other corrections to the HtmlHelper methods and properties available in extension methods and subclasses. See https://github.com/aspnet/MusicStore/blob/dev/src/MusicStore.Spa/Helpers/AngularHtmlHelper'T.cs for an example of current ugly workarounds for the general issue.

[dougbu]

Small update related to the AngularHtmlHelper<TModel> class: The GenerateId() method should not need to be public. For one thing Id() is a direct and public wrapper around this method. Further ViewData.TemplateInfo.GetFullHtmlFieldName() is already public though admittedly it returns a string and does not HTML encode that value. Most importantly GenerateIdFromName() is what really should be used (see #704) and it's also public.

[DamianEdwards]

Thanks, feel free to fix it for me :)