解读ASP.NET 5 & MVC6系列教程（13）：TagHelper

@Html.LabelFor(model => model.FullName)
@Html.EditFor(model => model.FullName)
@Html.ValidationMessageFor(model => model.FullName)

@addTagHelper "*, Microsoft.AspNet.Mvc.TagHelpers" /* 这里需要首先引用TagHelper所在的命名空间 */

<label asp-for="FullName" class="control-label col-md-2"></label>
<div class="col-md-10">
<input asp-for="FullName" class="form-control" />
<span asp-validation-for="FullName"></span>
</div>

asp-for

asp-controller

asp-action

{0:yyyy-MM-dd}

{0:yyyy-MM-ddTHH:mm:ss.fffK}

{0:yyyy-MM-ddTHH:mm:ss.fff}

{0:HH:mm:ss.fff}

<link rel="stylesheet"
href="//ajax.aspnetcdn.com/ajax/bootstrap-touch-carousel/0.8.0/css/bootstrap-touch-carousel.css"
asp-fallback-href="~/lib/bootstrap-touch-carousel/css/bootstrap-touch-carousel.css"
asp-fallback-test-class="carousel-caption"
asp-fallback-test-property="display"
asp-fallback-test-value="none" />

carousel-caption

display

none

<link rel="stylesheet" href="//ajax.aspnetcdn.com/ajax/bootstrap-touch-carousel/0.8.0/css/bootstrap-touch-carousel.css" />
<meta name="x-stylesheet-fallback-test" class="carousel-caption" />
<script>
!function (a, b, c) {
var d, e = document,
f = e.getElementsByTagName("SCRIPT"),
g = f[f.length - 1].previousElementSibling,
h = e.defaultView && e.defaultView.getComputedStyle ? e.defaultView.getComputedStyle(g) : g.currentStyle;

if (h && h[a] !== b) {
for (d = 0; d < c.length; d++) {
e.write('<link rel="stylesheet" href="' + c[d] + '"/>')
}
}
}("display", "none", ["\/lib\/bootstrap-touch-carousel\/css\/bootstrap-touch-carousel.css"]);
</script>

class="carousel-caption"

script

carousel-caption

display

none

none

document.getElementsByTagName("SCRIPT")

SCRIPT

meta

script

<script src="//ajax.aspnetcdn.com/ajax/jquery/jquery-1.10.2.min.js"
asp-fallback-src="~/lib/jquery/jquery.min.js"
asp-fallback-test="window.jQuery">
</script>

<script src="//ajax.aspnetcdn.com/ajax/jquery/jquery-1.10.2.min.js">
</script>
<script>(window.jQuery||document.write("<script src=\"\/lib\/jquery\/jquery.min.js\"><\/script>"));</script>

script

<environment names="Development">
<script src="~/lib/jquery/jquery.js"></script>
<script src="~/lib/bootstrap/js/bootstrap.js"></script>
<script src="~/lib/hammer.js/hammer.js"></script>
<script src="~/lib/bootstrap-touch-carousel/js/bootstrap-touch-carousel.js"></script>
</environment>
<environment names="Staging,Production"><script src="//ajax.aspnetcdn.com/ajax/jquery/jquery-1.10.2.min.js"
asp-fallback-src="~/lib/jquery/jquery.min.js"
asp-fallback-test="window.jQuery">
</script>
<script src="//ajax.aspnetcdn.com/ajax/bootstrap/3.0.0/bootstrap.min.js"
asp-fallback-src="~/lib/bootstrap/js/bootstrap.min.js"
asp-fallback-test="window.jQuery">
</script>
<script src="//ajax.aspnetcdn.com/ajax/hammer.js/2.0.4/hammer.min.js"
asp-fallback-src="~/lib/hammer.js/hammer.js"
asp-fallback-test="window.Hammer">
</script>
<script src="//ajax.aspnetcdn.com/ajax/bootstrap-touch-carousel/0.8.0/js/bootstrap-touch-carousel.js"
asp-fallback-src="~/lib/bootstrap-touch-carousel/js/bootstrap-touch-carousel.js"
asp-fallback-test="window.Zepto">
</script>
</environment>

IHostingEnvironment

EnvironmentName

Microsoft.AspNet.Razor.Runtime.TagHelpers.ITagHelper

public interface ITagHelper
{
int Order { get; }
Task ProcessAsync(TagHelperContext context, TagHelperOutput output);
}

TagHelper

Process

public class ATagHelper : TagHelper
{
[Activate]
public IUrlHelper UrlHelper { get; set; }

public string Controller { get; set; }

public string Action { get; set; }

public override void Process(TagHelperContext context, TagHelperOutput output)
{
if (Controller != null && Action != null)
{
var methodParameters = output.Attributes.ToDictionary(attribute => attribute.Key,
attribute => (object)attribute.Value);

// 删除所有的attributes，因为路由里已经可以自动生成了
output.Attributes.Clear();

output.Attributes["href"] = UrlHelper.Action(Action, Controller, methodParameters);

output.PreContent.SetContent("My ");
}
}
}

[TargetElement("p")]
public class AutoLinkerTagHelper : TagHelper
{
public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
{
var childContent = await context.GetChildContentAsync();

// Find Urls in the content and replace them with their anchor tag equivalent.
output.Content.SetContent(Regex.Replace(
childContent.GetContent(),
@"\b(?:https?://|www\.)(\S+)\b",
"<strong><a target=\"_blank\" href=\"http://$0\">$0</a></strong>"));
}
}

<p condition="Model.Approved" >© @Model.CopyrightYear - My ASP.NET Application</p>

[TargetElement("div")]
[TargetElement("style")]
[TargetElement("p")]
public class ConditionTagHelper : TagHelper
{
public bool? Condition { get; set; }

public override void Process(TagHelperContext context, TagHelperOutput output)
{
// 如果设置了condition，并且该值为false，则不渲染该元素
if (Condition.HasValue && !Condition.Value)
{
output.SuppressOutput();
}
}
}

public class WebsiteInformationTagHelper : TagHelper
{
public WebsiteContext Info { get; set; }

public override void Process(TagHelperContext context, TagHelperOutput output)
{
output.TagName = "section";
output.PostContent.SetContent(string.Format(
"<p><strong>Version:</strong> {0}</p>" + Environment.NewLine +
"<p><strong>Copyright Year:</strong> {1}</p>" + Environment.NewLine +
"<p><strong>Approved:</strong> {2}</p>" + Environment.NewLine +
"<p><strong>Number of tags to show:</strong> {3}</p>" + Environment.NewLine,
Info.Version.ToString(),
Info.CopyrightYear.ToString(),
Info.Approved.ToString(),
Info.TagsToShow.ToString()));
output.SelfClosing = false;
}
}

website-information

info

<website-information info="new WebsiteContext {
Version = new Version(1, 1),
CopyrightYear = 1990,
Approved = true,
TagsToShow = 30 }"/>

p

section

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