ValidationSummaryTagHelper for prefix only

[wutever0]

Is this a Bug or Feature request?:

Feature Request

Steps to reproduce (preferably a link to a GitHub repo with a repro project):

1 - Sometimes you have two forms on the page, each one submitted to a different action. e.g. a LoginRegister page split into two with a form for Login and another form for Register.
2 - Each action would be model-binded to a separate form model. e.g. LoginFormModel and RegisterFormModel
3 - Each form would have a Validation Summary

Description of the problem:

1 - If the form being submitted is invalid, the Validation Summary of both forms would include the validation error messages.
2 - There is no way of setting the Validation Summary to display messages for only the fields in its form or to display error messages only for model keys with a specific prefix (e.g. "Login" or "LoginFormInput" )

Version of Microsoft.AspNetCore.Mvc or Microsoft.AspNetCore.App or Microsoft.AspNetCore.All:

Microsoft.AspNetCore.App version is v2.1.1

[mkArtakMSFT]

Thanks for contacting us, @wutever0.
@javiercn, can you please look into this? Thanks!

[javiercn]

Thanks for contacting us @wutever0.

Can you share a small project on github reproducing the issue? That will allow us to have all the information in order to help you.

[wutever0]

Thank you @javiercn
I've created a quick sample here (https://github.com/wutever0/ValidationSummaryExample) based on something I was working on.

I also added a Readme to explain a bit more what is going on.

Hope this helps!

[javiercn]

I've taken a look at the repro project. Having different models for rendering the views and binding the models is not very well supported by MVC. It can be made to work, but it requires additional work.

The normal recommendation is to have the same model for rendering the views and binding the data to actions. When it comes to the validation summary, it seems that we have a feature gap here. It's important to notice that this works with client validation, although most likely it's just a side effect of how it's implemented.

We'll consider this feature during the next release planning period and update the status of this issue accordingly. To help us prioritize this feature correctly, please make sure you provide as much information as possible about the scenarios and their importance.

[wutever0]

Thank you @javiercn

Having different models for rendering the views and binding the models is not very well supported by MVC. It can be made to work, but it requires additional work.

The normal recommendation is to have the same model for rendering the views and binding the data to actions.

I just felt it was cleaner and unfortunately having the same model for rendering views and binding data to actions comes with its own set of issues.
In my scenario I would not be able to use DataAnnotations like Required on the model properties as only a subset of the model is involved in one action and another subset in another action but both would trigger invalid model state if I submit the whole model without filling it all in.
Having better support for different models is something definitely to look forward to.

To help us prioritize this feature correctly, please make sure you provide as much information as possible about the scenarios and their importance.

The current scenario of having a Login Form and a Register Form may be the clearest example as both login and register are completely separate functions (you do one or the other - not both).
I can't think of other specific scenarios but generally any views that have separate forms with their own validation summaries. The individual forms would have to be distinct enough so that they wouldn't logically use one validationsummary instead or just structured in a way where having separate validationsummaries would be easier for a user.

About importance I wouldn't say it's super important but it would definitely make the TagHelpers and HtmlHelpers more complete.