TagHelpers

[dotnet]

TagHelpers

[bricelam]

The tag helper documentation lives on the ASP.NET doc site.

[rowanmiller]

I think this refers to the Getting Started with ASP.NET 5 article we have. I'm personally not a fan of tag helpers, which is probably why they aren't used in the tutorial... but I agree being consistent with the template is a good idea.

[Eilon]

Should consult with @DamianEdwards on the best practices here.

[Rick-Anderson]

http://docs.asp.net/projects/mvc/en/latest/views/tag-helpers/authoring.html
http://docs.asp.net/projects/mvc/en/latest/views/tag-helpers/intro.html
Early feedback on my two TH articles is great. Run through my TH tutorials and I'm sure you'll love them.

[rowanmiller]

I have no problem adjusting the article to use tag helpers, that is definitely the right thing to do from a consistency point of view. I'm about to update everything to Beta 8 so I will do that at the same time.

Regarding liking tag helpers... for me personally it makes it too hard to distinguish between code and html. The thing I love about razor is that it's really clear what is code and it's just the same C# I write everywhere else in my application. With tag helpers that is completely obscured away.

[Rick-Anderson]

Read my intro doc - if you're using the default or light theme, TH/C# code is in a bold purple font. If you’re using the “Dark” theme the font is bold teal. I won't repeat the other advantages here, but I'm confident after using TH you'll grow to love them.

[rowanmiller]

GitHub doesn't know about them so I lose all that context when I'm looking at diffs, PR's etc. That's not my main issue though, if I look at this piece of markup... I have no idea what it's doing. If it was just calling APIs though I could go look at them, read Intellisense, etc.

        <environment names="Development">
            <link rel="stylesheet" href="~/lib/bootstrap/css/bootstrap.css" />
            <link rel="stylesheet" href="~/lib/bootstrap-touch-carousel/css/bootstrap-touch-carousel.css" />
            <link rel="stylesheet" href="~/css/site.css" />
        </environment>

BTW I'm not saying they don't provide value and that there aren't a bunch of folks who will like them... I'm just not one of them. I just want C# code and no magic/abstractions.

[rowanmiller]

@Rick-Anderson quick question, how do use the asp-for when I accessing something in a for loop? It looks like the default scope is to try and access the supplied item from Model but in this case I'm enumerating over the results of the model.

Here is the code, see where I'm trying to replace @Html.DisplayFor(modelItem => item.BlogId) with a tag helper.

    @foreach (var item in Model)
    {
        <tr>
            <td>
                <label asp-for="BlogId" />
                @Html.DisplayFor(modelItem => item.BlogId)
            </td>
            <td>
                @Html.DisplayFor(model => item.Url)
            </td>
        </tr>
    }

[Rick-Anderson]

@NTaylorMullen @rynowak can you answer @rowanmiller question?

[NTaylorMullen]

@rowanmiller You can do: <label asp-for="@item.BlogId"></label>

[Rick-Anderson]

@NTaylorMullen should that go in authoring TH or advanced?

[DamianEdwards]

You put an @ in front of the expression, then you can point it to whatever you like: asp-for="@item.BlogId"

[NTaylorMullen]

@Rick-Anderson Not authoring, it's more of a usage behavior for ModelExpression properties which are used by Mvc TagHelpers.

[dougbu]

We should not recommend foreach with expressions such as @item.BlogId or lambdas such as model => item.Url in general. They work fine in this display-only scenario but a generated <input> or <label> will have incorrect id or for attributes (respectively) and won't be bound correctly on submission. Need to mess with ViewData.TemplateInfo.HtmlFieldPrefix when using foreach. That's less straightforward than:

    @for (var i = 0; i < Model.Count; i++)
    {
        <tr>
            <td>
                <label asp-for="@Model[i].BlogId" />
                @Html.DisplayFor(model => model[i].BlogId)
            </td>
            <td>
                @Html.DisplayFor(model => model[i].Url)
            </td>
        </tr>
    }

[rowanmiller]

Yeah the @ prefix didn't work for me either, it just displayed blank data.

It's also super weird because anywhere else @item.BlogId within markup would be resolved to its actual value by running the code and then that value used in the tag. Now I need to know that @ behaves differently depending on whether it's in a normal HTML tag or a Tag Helper.

I've swapped over to tag helpers everywhere else in #45. I'll leave this section as-is for the moment.

[dougbu]

@rowanmiller @item.BlogId is still resolved to the expression's "actual value", just a bit later.

As soon as you type @ anywhere, Razor puts you in a C# context. The difference w/ asp-for is that you're already in a C# context, after someLambdaParameter => someLambdaParameter. (note the trailing period). After the @, you're in a different C# context -- instead after someLambdaParameter =>.

[rowanmiller]

This is done in 3eba324, aside from the for loop scenario being discussed here (where it sounds like tag helpers are not the right thing to use).