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Editorial Team
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Asked: 2026-05-29T20:52:49+00:00

I have an MVC3 app, using EF, where one table winds up in a

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I have an MVC3 app, using EF, where one table winds up in a lot of view models. It has a field that is normally not required. But, there is one situation (and one view) where it is required. I want both client and server validation for this field’s required-ness, in the one place where it IS required.

Now, I do not want to put the Required data annotation on the field, because then it will always be required. This would be true even on views where the field isn’t displayed for edit, which would result in a validation message the user couldn’t make go away.

I also am not looking for a RequiredIf validation attribute, because that doesn’t fit the design. The field is only required under one circumstance, and I don’t want to have to stick in an extra field from a superfluous table in all my view models, just for the sake of the dependency.

All I want is to be able to turn on required field validation for one field in one view, in an ad-hoc, not-based-on-DataAnnotations manner.

The way that immediately suggested itself to me was to specify the necessary data-val-* attributes when creating the markup for the field (through the HtmlAttributes object at the end of the HtmlHelper.TextBoxFor signature). If I understand correctly, this should cue JS unobtrusive validation to treat the field as required.

But this is … a little too much of a hack, seems to me. Unobtrusive validation support would be intruding into the higher-level code. Is there a more elegant way to do this? A jQuery Validation function call I can use to make what I want to have happen, happen?

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1 Answer

  1. Editorial Team

    Not only does that data-val approach have a codes smell, it’s also unreliable because the end user may be using a client that doesn’t do unobtrusive validation. client-side validation is candy, that’s nice to have. You must always have server-side validation.

    This is the problem you have when you use your data model for your view model. The correct approach is to create seperate view models for each view. You can get by with sharing View Models and creating seperate view models for only those views that are different. In either case, if you have a unique view, it needs its own unique view model.

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