下面的代码复制了我尝试在新的 ASP.NET Core 3.0 API 项目中创建的某些扩展的错误。using ClassLibrary1;using Microsoft.AspNetCore.Hosting;using Microsoft.Extensions.Hosting;namespace WebApplication1{  public class Program  {    public static void Main(string[] args)    {      CreateHostBuilder(args).Build().Run();    }    public static IHostBuilder CreateHostBuilder(string[] args) =>        Host.CreateDefaultBuilder(args)            .ConfigureWebHostDefaults(webBuilder =>            {              webBuilder.UseStartup<Startup>();              webBuilder.ConfigureAppConfiguration((context, config) =>              {                // this works fine                var env = context.HostingEnvironment;              });              webBuilder.CustomConfigureAppConfiguration();            })            .ConfigureAppConfiguration((context, config) =>            {              // this works fine              var env = context.HostingEnvironment;            })            .CustomConfigureAppConfiguration();  }}该类Extensions需要位于不同的项目中。在同一个主项目中似乎工作正常。using Microsoft.AspNetCore.Hosting;using Microsoft.Extensions.Hosting;// This project can be either netstandard2.0 or netcoreapp3.0namespace ClassLibrary1{  public static class Extensions  {    public static IWebHostBuilder CustomConfigureAppConfiguration(this IWebHostBuilder hostBuilder)    {      hostBuilder.ConfigureAppConfiguration((context, config) =>      {        // this fails with System.MissingMethodException: 'Method not found: 'Microsoft.AspNetCore.Hosting.IHostingEnvironment Microsoft.AspNetCore.Hosting.WebHostBuilderContext.get_HostingEnvironment()'.'        var env = context.HostingEnvironment;      });      return hostBuilder;    }它仅在运行时失败，并且仅在访问HostingEnvironment. 当删除/评论var env = context.HostingEnvironment;作业时，我仍然可以在调试中检查和查看它。知道我在这里缺少什么吗？