c# - 如何解决 IURLHelper 的问题(在 startup.cs 上添加单例不起作用)ASP.NET Core 2.2

Question

我正在尝试为我的网站创建分页。我正在从 Adam Freeman 的书“ASP.NET Core 2”中学习。这些行:
IUrlHelper urlHelper = urlHelperFactory.GetUrlHelper(ViewContext);
TagBuilder result = new TagBuilder("div");

返回空值。有什么问题？

这是一个 asp.net core 2.2 应用程序。

无效的代码:

public override void Process(TagHelperContext context, TagHelperOutput output)
{
     IUrlHelper urlHelper = urlHelperFactory.GetUrlHelper(ViewContext);
     TagBuilder result = new TagBuilder("div");
     for (int i = 1; i <= PageModel.TotalPages; i++)
     {
          TagBuilder tag = new TagBuilder("a");
          tag.Attributes["href"] = urlHelper.Action(PageAction, new { ProductPage = i });
          tag.InnerHtml.AppendHtml(tag);
     }
     output.Content.AppendHtml(result.InnerHtml);
}

我将其添加到 startup.cs 中:

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
services.AddScoped<IUrlHelper>(factory =>
{
     var actionContext = factory.GetService<IActionContextAccessor>().ActionContext;
     return new UrlHelper(actionContext);
});

我添加了一个单元测试，它应该返回一个 <a href="test/pageX"></a>对于所有页面，但它什么都不返回。

Answer 1

您错误地将 anchor 添加到自身，而是尝试将其添加到容器 div

TagBuilder result = new TagBuilder("div");
for (int i = 1; i <= PageModel.TotalPages; i++)
{
     TagBuilder tag = new TagBuilder("a");
     tag.Attributes["href"] = urlHelper.Action(PageAction, new { ProductPage = i });     
     // tag was being added to itself, rather add it the container `div`
     // tag.InnerHtml.AppendHtml(tag);
     result.InnerHtml.AppendHtml(tag);

}