如何创建从标准.Net Core脚本标记助手继承的脚本标记助手 [英] How to create a script tag helper that inherits from the standard .Net Core script tag helper

问题描述

我维护着一个大型的遗留ASP.NET MVC应用程序，该应用程序最近已转换为.Net Core。

I maintain a large legacy ASP.NET MVC application, which was recently converted to .Net Core.

我需要为我们的JavaScript和CSS文件引入缓存清除功能。我赞赏使用新的.Net Core脚本标记帮助器上的 asp-append-version = true 属性可以轻松完成此操作。

I need to introduce cache busting for our JavaScript and CSS files. I appreciate this can easily be done using the asp-append-version="true" attribute on the new .Net Core script tag helper.

但是，我的应用程序在100多个位置中具有脚本标签。在所有这些位置添加该属性将涉及大量页面，这意味着需要进行大量回归测试。

However, my application has script tags in over a 100 places. Adding the attribute in all those places will touch large numbers of pages, which means a lot of regression testing.

是否有一种方法可以创建一个新的继承自脚本标记的助手从.Net Core脚本标签帮助程序中获取，并且该属性始终具有 asp-append-version = true 属性？

Is there a way to create a new script tag helper that inherits from the .Net Core script tag helper, and that always has the asp-append-version="true" attribute? That will give me cache busting without having to update lots of files.

推荐答案

... create一个从.Net Core脚本标记助手继承而来的新脚本标记助手，并且始终具有asp-append-version = true属性？

...create a new script tag helper that inherits from the .Net Core script tag helper, and that always has the asp-append-version="true" attribute?

代码（在GitHub上查看）

Code (View on GitHub)

using System.Linq;
using System.Text.Encodings.Web;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc.Routing;
using Microsoft.AspNetCore.Mvc.TagHelpers;
using Microsoft.AspNetCore.Razor.TagHelpers;
using Microsoft.Extensions.Caching.Memory;

namespace AspNetCoreScriptTagHelperOverride
{
    [HtmlTargetElement("script")] // A
    public class MyScriptTagHelper : ScriptTagHelper
    {
        public MyScriptTagHelper(
            IHostingEnvironment env,
            IMemoryCache cache,
            HtmlEncoder html,
            JavaScriptEncoder js,
            IUrlHelperFactory url) : base(env, cache, html, js, url) { } // B

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            const string appendVersion = "asp-append-version";
            if (!context.AllAttributes.Any(a => a.Name == appendVersion))
            {
                var attributes = new TagHelperAttributeList(context.AllAttributes);
                attributes.Add(appendVersion, true);
                context = new TagHelperContext(attributes, context.Items, context.UniqueId);
            } // E

            base.AppendVersion = true; // C
            base.Process(context, output); // D
        }
    }
}

说明

• A：将 TagName 设置为脚本 。


• B：实现基本构造函数。


• C：硬代码 AppendVersion 为true。


• D：调用基类的 Process 。


• E ：克服 AttributeMatcher.TryDetermineMode



Explanation

• A: Set the TagName to "script".
• B: Implement the base constructor.
• C: Hard code AppendVersion to true.
• D: Call the base class's Process.
• E: Overcome AttributeMatcher.TryDetermineMode

在 _ViewImports.cshtml 中删除现有的标签帮助程序并添加您的替代项。

@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@removeTagHelper Microsoft.AspNetCore.Mvc.TagHelpers.ScriptTagHelper, Microsoft.AspNetCore.Mvc.TagHelpers
@addTagHelper *, AspNetCoreScriptTagHelperOverride

Be确保使用您的程序集的名称。

Be sure to use the name of your assembly.

完成后，只要有脚本标记帮助器，您的代码就会执行。例如，下面两个都将 AppendVersion 设置为 true 。

Once that is done, your code will execute wherever there is a script tag helper. For instance, both of the following will have AppendVersion set to true.

<script src="~/js/site.js"></script>
<script src="~/js/site.js" asp-append-version="true"></script>
<script src="~/js/site.js" asp-append-version="false"></script>

这将是结果HTML：

<script src="/js/site.js?v=4q1jwFhaPaZgr8WAUSrux6hAuh0XDg9kPS3xIVq36I0"></script>





另请参见





https://github.com/aspnet/Mvc/ blob / dev / src / Microsoft.AspNetCore.Mvc.TagHelpers / ScriptTagHelper.cs

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