TagHelper [asp-validation-for] doesn't work on server side

[John0King]

This is the code i write:

<input asp-for="Title" class="form-control" />
<span asp-validation-for="Title" class="text-danger"  />

And this is the code that Generated:

<input name="Title" class="form-control input-validation-error" id="Title" type="text" value="sfdsfd" data-val="true" data-val-length-max="2" data-val-length="字段 Title 必须是最大长度为 2 的字符串。">
 <span class="text-danger field-validation-error" data-valmsg-replace="true" data-valmsg-for="Title">
</span>

[dougbu]

If the actual generated HTML is <span ... />, everything is behaving as expected. The error message isn't visible because the self-closing element has no body.

Change the source to

...
<span asp-validation-for="Title" class="text-danger"></span>

[John0King]

Is this a bug of visual studio web tools ?

[dougbu]

We've had a few discussions related to this experience and aspnet/Tooling#398 remains open. But the onus today is on .cshtml authors; they must not write a normal HTML element as self-closing.

Side note: aspnet/Tooling#398 is about the opposite problem: VS does not warn when users write a void element with an end tag e.g. <input ...></input>.

[John0King]

I think Razor View is missing some usefule method:

//get  every error message of  Model's property
public IEnumerable<string> GetModelErrorsFor( Action<model> action )
// get single error message of Model's property , sometimes i want  show only one error
public string GetFirstModelErrorFor(Action<model> action)
// get validation-summary
public IEnumerable<string> GetModeErrors( ValidationSummary options )

// and also  DisplayNameFor 

those method work like HtmlHelpers or TagHelpers , but they only return pure string rather than full HTML mark; So we can use them in any cases!

[Eilon]

Moving to backlog.