CODEWITHSUNDEEP
asp.net-coreasp.net-core-tag-helpers
Bob.at.Indigo.Health
Bob.at.Indigo.Health

Reputation: 11905

Pass info between tag helpers?

I am writing a set of tag helpers that target, for example, <form> and <input> elements. I want to add a custom attribute to the <form> element, and retrieve the value of that attribute in the contained <input> element. So, if my HTML looks like this:

<form xx-value='123'>
  <input asp-for='Something' />
</form>

then in my InputTagHelper I would want to retrieve the value 123 that was specified for the xx-value attribute.

Is there a designed-in way to pass data like this between tag helpers?

Consider the case where I have this markup:

<form xx-value='123'>
  <input asp-for='Something' />
</form>
<form>
  <input asp-for='SomethingElse' />
</form>

In this case, the first invocation of the InputTagHelper would get the value 123. But the second invocation of the InputTagHelper would get a value of 0 since its parent <form> tag didn't specify the magic xxx-value attribute.

Upvotes: 1

Views: 925

Answers (1)

Bob.at.Indigo.Health
Bob.at.Indigo.Health

Reputation: 11905

The simple answer (which doesn't work for <form> and <input> tags - see blow) is for the "parent" tag helper to store the value in the context.Items dictionary and for the "child" tag helper(s) to retrieve the value from that same dictionary. A Google search for "child tag helper" yields many examples of this scheme.

The problem with this answer (in the context of the OP) is that, for some reason, the <form> tag helper executes after its child <input> tag helper. So, rather than receiving the value from the parent FormTagHelper, the InputTagHelper discovers that the context.Items dictionary is empty.

I created this SO post to ask about that weird behavior.

Upvotes: 2

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