can a mvc custom html helper inherit a base helper?

Question

So I want to be able to add a data- attribute to my @HTML.Listbox html helper in the razor syntax. My understanding is that I can't do this without creating my own customer html helper.

My question is, is there a way to create a custom html helper but basically inherit everything from the base @HTML.Listbox and then just add the ability to add a data- attribute? Does something like already exist?

Thanks in advance!

Answer 1

All the in-built HtmlHelper methods for generating form controls have overloads the allow you to add html attributes.

For the ListBoxFor() method, the overloads are documented here. In your case its

@Html.ListBoxFor(m => m.someProperty, Model.Options, new { data_someName = "someValue" })

which will generate

<select name="someProperty" id="someProperty" multiple="multiple" data-someName="someValue"> .... </select>

Note when adding attributes containing a hyphen, you must use an underscore in the method (and the method will convert it to a hyphen in the rendered html).

You can also create your own HtmlHelper extension methods that can generate more complex html including automatically adding fixed attributes, for example you might create a BootstrapTextBoxFor() helper that automatically adds a class="form-control" attribute

public static MvcHtmlString BootstrapTextBoxFor<TModel, TValue>(this HtmlHelper<TModel> helper, 
Expression<Func<TModel, TValue>> expression, object htmlAttributes)
{
    IDictionary<string, object> attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
    attributes.Add("class", "form-control");
    ... other 'fixed' attributes as required
    return InputExtensions.TextBoxFor(helper, expression, attributes);
}

Some other example are shown in the the answers here and here.