replacement for html.GetUnobtrusiveValidationAttributes html.GetClientValidationRules

[omuleanu]

hi
in mvc 5 there was html.GetUnobtrusiveValidationAttributes
in rc1 I think there was html.GetClientValidationRules
now, I can't find anything that will return the same

I'm developing a custom helper and I need to get the client validation attributes

[Eilon]

@dougbu ?

[Eilon]

@rynowak I think you worked in this area too?

[dougbu]

In RC1, DefaultHtmlGenerator had a GetClientValidationRules() method. That class now exposes a AddValidationAttributes() method with a similar purpose. Both methods were / are virtual. But neither are / were exposed through IHtmlHelper.

For this use case, I suggest extending IHtmlHelper with new methods. Those methods can examine / update the TagBuilder that TextBox() and so on return.

public IHtmlContent MyTextBox(
    this IHtmlHelper helper,
    string expression,
    object value,
    string format,
    object htmlAttributes)
{
    var content = helper.TextBox(expression, value, format, htmlAttributes);
    var tagBuilder = content as TagBuilder;
    if (tagBuilder != null)
    {
        tagBuilder.AddCssClass("classy");
    }

    return content;
}

[omuleanu]

so is there a way now to get the validation attributes ?
imagine I have something like this:

public static IHtmlContent About<T>(this IHtmlHelper helper)
{
   // how to get a Dictionary<string, string> 
   // of html <attribute, value> needed for jquery.validate unobtrusive
}

[dougbu]

If looking for the attributes a specific helper would add, could do something like I showed above but with

var dictionary = tagBuilder.Attributes
    .Where(item => item.Key.StartsWith("data-", StringComparison.OrdinalIgnoreCase))
    .ToDictionary(keySelector: item => item.Key, elementSelector: item => item.Value);

Could also subclass DefaultHtmlGenerator e.g.

public class MyHtmlGenerator : DefaultHtmlGenerator
{
    public MyHtmlGenerator(
        IAntiforgery antiforgery,
        IOptions<MvcViewOptions> optionsAccessor,
        IModelMetadataProvider metadataProvider,
        IUrlHelperFactory urlHelperFactory,
        HtmlEncoder htmlEncoder,
        ClientValidatorCache clientValidatorCache)
        : base(
              antiforgery,
              optionsAccessor,
              metadataProvider,
              urlHelperFactory,
              htmlEncoder,
              clientValidatorCache)
    {
    }

    public new void AddValidationAttributes(...)
    {
        // ...
    }
}

Then place MyHtmlGenerator in DI and use it from your extension methods e.g.

var generator = helper.ViewContext.HtmlContext.RequestServices.GetRequiredService<IHtmlGenerator>() as MyHtmlGenerator

Unfortunately ClientValidatorCache was placed it in an .Internal namespace. This implies nothing about it can be relied upon. Might be better to create a wrapper class that delegates to the default IHtmlGenerator but is itself registered without reference to that interface.

[omuleanu]

ok, so the way to get the validation attributes now is to generate an editor (textbox, hidden input), cast it as TagBuilder and after filter the TagBuilder.Attributes, will this get easier in the future ?

[Eilon]

I don't believe that inspecting the TagBuilder attributes produced by a random other helper is a recommended approach.

@dougbu can we just add an interface / API that exposes the required information? I don't think any of the examples given here are supported or recommended...

[dougbu]

@Eilon sure, we can add an interface that DefaultHtmlGenerator would also implement. We can't make AddValidationAttributes() public but can call that from a new method.

@omuleanu exactly what information do you need? In particular would a new method similar to the existing AddValidationAttributes() be right for your custom helper?

[omuleanu]

I need to get the collection of js validation attributes, this method was present in mvc5, 4, 3
this how it is defined in mvc 5:

//
// Summary:
//     Gets the collection of unobtrusive JavaScript validation attributes using the
//     specified HTML name attribute and model metadata.
//
// Parameters:
//   name:
//     The HTML name attribute.
//
//   metadata:
//     The model metadata.
//
// Returns:
//     The collection of unobtrusive JavaScript validation attributes.
public IDictionary<string, object> GetUnobtrusiveValidationAttributes(string name, ModelMetadata metadata);

[omuleanu]

@dougbu is this going to be implemented any time soon ?

[dougbu]

@omuleanu I don't know.

@danroth27, @Eilon this doesn't have a milestone and seems to be missing all labels. Suggest this would be an Enhancement.