我刚刚创建了一个新的ASP.NET Core3.1 Web API，这是我第一次运行它。 我添加了一些endpoint和启动代码，并用一些额外的配置改变了启动，但是程序根本没有运行。 我不确定我的启动是否影响了这一点，但我看不到我添加的任何东西会破坏启动顺序。

我得到的例外是:

System.NullReferenceException: Object reference not set to an instance of an object.
   at -snip-.Startup.Configure(IApplicationBuilder app, IWebHostEnvironment env) in C:\-snip-\Startup.cs:line 56
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.<Build>b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass13_0.<UseStartup>b__2(IApplicationBuilder app)
   at Microsoft.ApplicationInsights.AspNetCore.ApplicationInsightsStartupFilter.<>c__DisplayClass2_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter.<>c__DisplayClass0_0.<Configure>g__MiddlewareFilterBuilder|0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)
   at Microsoft.Extensions.Hosting.Internal.Host.StartAsync(CancellationToken cancellationToken)
   at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token)
   at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token)
   at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.Run(IHost host)
   at -snip-.Program.Main(String[] args) in C:\-snip-\Program.cs:line 16

启动类

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            services.AddCors();
            services.AddApplicationInsightsTelemetry();
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("", new OpenApiInfo
                {
                    Title = "",
                    Version = "v1"
                });
            });

            services.AddTransient<IClientSettingsBlobService, ClientSettingsBlobService>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            
            string origins = Configuration["CorsAllowedOrigins"];
            string[] originsArray = origins.Split(',', StringSplitOptions.RemoveEmptyEntries).Select(o => o.Trim()).ToArray();
            app.UseCors(b => b.AllowAnyMethod().AllowAnyHeader().AllowCredentials().WithOrigins(originsArray));
            app.UseHttpsRedirection();
            app.UseAuthentication();
            app.UseAuthorization();

            
            app.UseSwagger();
            app.UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "");
            });

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
        }
    }