ASP.NET Core 2中类库中的依赖注入

Question

我有一个ASP.NET核心类库，它依赖于引用dll的项目中的依赖项注入。但是当我尝试获取服务时，服务始终为空。

这是我到目前为止唯一可行的设计，因为我想我不能直接在类库中设置依赖服务。

班级图书馆：

@include "join"
{
  n=split($0, a, " ")
  s=join(a, 1, n-1)
  b[$NF s]=$0
}
END{
  n=asorti(b,c);
  for(j=1;j<=n;j++) print b[c[j]]
}

在引用类库的项目中启动：

public interface IHtmlResourceLocalizer
{
    string Get(string cultureCode, string name);
    string Get(CultureInfo culture, string name);
}

public class HtmlResourceLocalizer : IHtmlResourceLocalizer
{
    private readonly IHostingEnvironment _env;
    private readonly IHttpContextAccessor _context;

    public HtmlResourceLocalizer(IHostingEnvironment env, IHttpContextAccessor context)
    {
        _env = env;
        _context = context;
    }

    public string Get(string cultureCode, string name) { return Get(new CultureInfo(cultureCode), name); }

    public string Get(CultureInfo culture, string name)
    {
        string result = string.Empty, filename = name + "." + culture.Parent.Name + ".cshtml";
        string path = Path.Combine(this.Env.ContentRootPath, "Views", "Resources", filename);

        if (File.Exists(path))
        {
            IRazorViewEngine engine = _context.HttpContext.Features.Get<IRazorViewEngine>();
            ITempDataProvider temp = _context.HttpContext.Features.Get<ITempDataProvider>();

            ViewRenderUtility util = new ViewRenderUtility(engine, temp, _context.HttpContext.RequestServices);

            result = util.ViewToString(filename, null).Result;
        }
        else
        {
            throw new FileNotFoundException("Could not find file \"" + path + "\"");
        }

        return result;
    }

    public IHostingEnvironment Env { get { return _env; } }
}

查看：

public void ConfigureServices(IServiceCollection services)
{
    services.AddLocalization(options => options.ResourcesPath = "Resources");
    services.AddSingleton<IHtmlResourceLocalizer, HtmlResourceLocalizer>();
    services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
    services.AddSingleton<IRazorViewEngine, RazorViewEngine>();
    services.AddSingleton<AppHelper>();

    services.AddMvc()
        .AddViewLocalization(Microsoft.AspNetCore.Mvc.Razor.LanguageViewLocationExpanderFormat.Suffix)
        .AddDataAnnotationsLocalization();
}