最近做的TagHelper项目要从原来的ASP.NET 5 Beta 4升级到Beta 5,特地整理了升级后的变化:
<img asp-file-version="true" src="~/images/my_cool_image.png" />
<a asp-action="Edit" asp-route-id="@index">Edit</a>
在该类中定义如下:
public class AnchorTagHelper : TagHelper{ PRivate const string RouteValuesDictionaryName = "asp-all-route-data"; private const string RouteValuesPrefix = "asp-route-"; /// <summary> /// Additional parameters for the route. /// </summary> [HtmlAttributeName(RouteValuesDictionaryName, DictionaryAttributePrefix = RouteValuesPrefix)] public IDictionary<string, string> RouteValues { get; set; } = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); ... }
这里只列出与该Dictionary属性相关的定义,主要是在该属性头上添加HtmlAttributeName并设置其DictionaryAttributePrefix。
[TargetElement("a", Attributes = ActionAttributeName)][TargetElement("a", Attributes = ControllerAttributeName)][TargetElement("a", Attributes = FragmentAttributeName)][TargetElement("a", Attributes = HostAttributeName)][TargetElement("a", Attributes = ProtocolAttributeName)][TargetElement("a", Attributes = RouteAttributeName)][TargetElement("a", Attributes = RouteValuesDictionaryName)][TargetElement("a", Attributes = RouteValuesPrefix + "*")]public class AnchorTagHelper : TagHelper{ private const string ActionAttributeName = "asp-action"; private const string ControllerAttributeName = "asp-controller"; private const string FragmentAttributeName = "asp-fragment"; private const string HostAttributeName = "asp-host"; private const string ProtocolAttributeName = "asp-protocol"; private const string RouteAttributeName = "asp-route"; private const string RouteValuesDictionaryName = "asp-all-route-data"; private const string RouteValuesPrefix = "asp-route-"; private const string Href = "href"; ...}
从上面可以看出,该TagHelper会应用到A tag上,并且这个tag上需要有asp-action, asp-controller, asp-fragment, asp-host, asp-protocol, asp-route, asp-all-route-data和asp-route-*这些attributes中一个或一个以上,否则该tag就会绑定到该TagHelper。在最后一个条件绑定中,使用了通配符*,这也是Beta5上支持的。比如
<a href="http://www.VEVb.com/liontone/">上善若水</a>
就不会被应用上AnchorTagHelper。
public class MyTagHelper : TagHelper{ [HtmlAttributeNotBound] [Activate] public IHtmlEncoder Encoder { get; set; } [HtmlAttributeNotBound] [Activate] public ViewContext ViewContext { get; set; }}
现在:
public class MyTagHelper : TagHelper{ public MyTagHelper(IHtmlEncoder encoder) { Encoder = encoder; } public IHtmlEncoder Encoder { get; } [HtmlAttributeNotBound] [ViewContext] public ViewContext ViewContext { get; set; }}
public class MyTagHelper : TagHelper{ public MyTagHelper(IHtmlEncoder encoder) { Encoder = encoder; } public IHtmlEncoder Encoder { get; } [HtmlAttributeNotBound] [ViewContext] public ViewContext ViewContext { get; set; }}
按照以前文章介绍,ViewContext对应TagHelper的Attribute是view-context,但其实我们不希望它成为Attribute,这时只需要加上HtmlAttributeNotBoundAttribute即可,在Visual Studio 2015中也不会有该Attribute的智能提示了。
public void Process(TagHelperContext context, TagHelperOutput output){ var nl = Environment.NewLine; var br = "<br />" + nl; output.PreElement.Append("This will appear before source element" + br); output.PreContent.Append(nl + "This will appear before source content" + br); output.PostContent.Append(br + "This will appear after source content" + nl); output.PostElement.Append(br + "This will appear after source element");}
在View上TagHelper:
<my-tag-helper> Content in source</my-tag-helper>
最后进过解析后生成到页面的内容是:
This will appear before source element<br /><my-tag-helper>This will appear before source content<br /> Content in source<br />This will appear after source content</my-tag-helper><br />This will appear after source element
上面是我在项目升级过程中遇到的问题,其实还有很多变化,需要大家根据自己项目情况来发现,具体beta5详细变化见这里。
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