如何在使用 TagHelpers 时突出显示导航栏菜单项 (Asp.Net.MVC6 6.0.0-rc1.0-final)

Question

我想在 asp.net 5 1.0.0-rc1-final 的菜单链接中生成 class="active"，以突出显示 [=35] 中导航栏的活动菜单=].
这里提出的解决方案：Original post by Prashant Adepu 在 Asp.Net.MVC 6.0.0 beta5 中工作正常。 然而在6.0.0 rc1 (asp.net 1.0.0 rc-1 final)中，似乎不可能使用[ViewContext]修饰因为这个属性不存在。
有解决办法吗？

1) 下面是对 rc-1 稍作修改的代码。
除 [ViewContext] 被拒绝 外，一切正常。如果没有此属性，viewContext 将在 运行 时间后为空。
2) 到运行你应该创建一个asp.net5 WebApplicationX，并在_ViewImports.cshtml.
中添加@addTagHelper "WebApplicationX.TagHelpers.MenuLinkTagHelper, WebApplicationX" 然后只需使用 <menulink controller-name="Home" action-name="About" menu-text="About"></menulink> 而不是常规 mvc <a asp-controller="Home" asp-action="Index">Home</a> Anchor.

using Microsoft.AspNet.Mvc;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Razor.Runtime.TagHelpers;
using Microsoft.AspNet.Razor.TagHelpers;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WebApplicationX.TagHelpers
{
    [HtmlTargetElement("menulink", Attributes = "controller-name, action-name, menu-text")]
    public class MenuLinkTagHelper : TagHelper 
    {
        public string ControllerName { get; set; }
        public string ActionName { get; set; }
        public string MenuText { get; set; }
        [ViewContext]                         //*** This is not allowed.***
        public ViewContext ViewContext { get; set; }

        public IUrlHelper _UrlHelper { get; set; }

        public MenuLinkTagHelper(IUrlHelper urlHelper)
        {
            _UrlHelper = urlHelper;
        }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            StringBuilder sb = new StringBuilder();

            string menuUrl = _UrlHelper.Action(ActionName, ControllerName);

            output.TagName = "li";

            var a = new TagBuilder("a");
            a.MergeAttribute("href", $"{menuUrl}");
            a.MergeAttribute("title", MenuText);
            a.InnerHtml.Append(MenuText);

            var routeData = ViewContext.RouteData.Values;
            var currentController = routeData["controller"];
            var currentAction = routeData["action"];

            if (String.Equals(ActionName, currentAction as string, StringComparison.OrdinalIgnoreCase)
                && String.Equals(ControllerName, currentController as string, StringComparison.OrdinalIgnoreCase))
            {
                output.Attributes.Add("class", "active");
            }

            output.Content.SetContent(a.ToString());
        }
    }
}

Answer 1

ViewContext 属性仍然存在。它在 Microsoft.AspNet.Mvc.ViewFeatures 中，而不是在 Microsoft.AspNet.Mvc.Rendering 中（ViewContext class 本身所在的位置）。确保选择正确的。您可以在此处查看示例：https://github.com/DannyvanderKraan/TagHelpers

Answer 2

感谢 Danny 的帮助，在重温原著后，您可以在下面找到 1.0.0-rc1-final 的工作代码

    using Microsoft.AspNet.Mvc;
    using Microsoft.AspNet.Mvc.Rendering;
    using Microsoft.AspNet.Mvc.ViewFeatures;                    //change for 1.0.0-rc1.0-final
    using Microsoft.AspNet.Razor.TagHelpers;
    using System;
    using System.Text;

namespace WebAppName.TagHelpers
{
    [HtmlTargetElement("menulink", Attributes = "controller-name, action-name, menu-text")]
    public class MenuLinkTagHelper : TagHelper
    {
        public string ControllerName { get; set; }
        public string ActionName { get; set; }
        public string MenuText { get; set; }
        [ViewContext]
        public ViewContext ViewContext { get; set; }

        public IUrlHelper _UrlHelper { get; set; }

        public MenuLinkTagHelper(IUrlHelper urlHelper)
        {
            _UrlHelper = urlHelper;
        }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            StringBuilder sb = new StringBuilder();

            string menuUrl = _UrlHelper.Action(ActionName, ControllerName);

            output.TagName = "li";

            var a = new TagBuilder("a");
            a.MergeAttribute("href", $"{menuUrl}");
            a.MergeAttribute("title", MenuText);
            a.InnerHtml.Append(MenuText);                    //change for 1.0.0-rc1.0-final

            var routeData = ViewContext.RouteData.Values;
            var currentController = routeData["controller"];
            var currentAction = routeData["action"];

            if (String.Equals(ActionName, currentAction as string, StringComparison.OrdinalIgnoreCase)
                && String.Equals(ControllerName, currentController as string, StringComparison.OrdinalIgnoreCase))
            {
                output.Attributes.Add("class", "active");
            }
            output.Content.Append(a);                    //change for 1.0.0-rc1.0-final
        }
    }
}