ASP.NET Core Web API端点访问遇HTTP Error 404问题求助

创建新的ASP.NET Core Web API项目后，在开发环境运行时出现HTTP Error 404. This localhost page can't be found.错误。尝试在Program.cs和ServiceExtension.cs中设置断点调试，但程序并未进入控制器类和服务类。

Program.cs 代码 #

var builder = WebApplication.CreateBuilder(args);

// Including the path for configuration file for the NLog configuration.
LogManager.LoadConfiguration(string.Concat(Directory.GetCurrentDirectory(), "/nlog.config"));

// Add services to the container.
builder.Services.ConfigureCors();
builder.Services.ConfigureIISIntegration();
builder.Services.ConfigureLoggerService();
builder.Services.ConfigureSqlContext(builder.Configuration);
builder.Services.ConfigureRepositoryManager();
builder.Services.ConfigureServiceManager(); 
builder.Services.AddControllers().AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly);


var app = builder.Build();
if(app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}
else
{
    app.UseHsts();
}
// Configure the HTTP request pipeline.

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseForwardedHeaders(new ForwardedHeadersOptions { ForwardedHeaders = ForwardedHeaders.All });
app.UseCors("CorsPolicy");
app.UseAuthorization();

app.MapControllers();

app.Run();

ServiceExtension.cs 代码 #

namespace CompanyEmployees.Extensions
{
    public static class ServiceExtensions
    {
        public static void ConfigureCors(this IServiceCollection services) =>
        services.AddCors(options =>
        {
        options.AddPolicy("CorsPolicy", builder => builder.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader());
        });

        public static void ConfigureIISIntegration(this IServiceCollection services) =>
            services.Configure<IISOptions>(options =>
            {
                //We are not adding any options becasue we are configuring for default ones
            });

        public static void ConfigureLoggerService(this IServiceCollection services) => services.AddSingleton<ILoggerManager, LoggerManager>();

        public static void ConfigureRepositoryManager(this IServiceCollection services) => services.AddScoped<IRepositoryManager, RepositoryManager>();

        public static void ConfigureServiceManager(this IServiceCollection services) => services.AddScoped<IServiceManager, ServiceManager>();

        public static void ConfigureSqlContext(this IServiceCollection services, IConfiguration configuration) => services.AddDbContext<RepositoryContext>(opts => opts.UseSqlServer(configuration.GetConnectionString("sqlconnection")));
    } 
}

控制器类代码 #

namespace CompanyEmployees.Presentation.Controllers
{
    [Route("api/companies")]
    [ApiController]
    public class CompaniesController : ControllerBase
    {
        private readonly IServiceManager _serviceManager;

        public CompaniesController(IServiceManager serviceManager)
        {
            _serviceManager = serviceManager;
        }

        [HttpGet]
        public IActionResult GetCompanies()
        {
            try
            {
                var companies = _serviceManager.CompanyService.GetAllCompanies(trackChanges: false);
                return Ok(companies);
            }
            catch
            {
                return StatusCode(500, "Internal Server Error");
            }
        }

    }
}

• 确认控制器程序集加载是否正确
  代码中使用AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly)加载控制器所在程序集，需先检查AssemblyReference类是否存在于CompanyEmployees.Presentation项目中。若该类不存在，程序集无法被正确识别，控制器也不会被注册。
  解决方式：要么在CompanyEmployees.Presentation项目中添加一个空的AssemblyReference类（仅用于标记程序集），要么直接替换为控制器类型获取程序集，比如typeof(CompaniesController).Assembly。

• 验证请求地址准确性
  确保访问地址为https://localhost:<端口号>/api/companies，代码中启用了UseHttpsRedirection，必须使用HTTPS协议，且不能遗漏api/companies路径。若访问根路径/，因无对应控制器，返回404属于正常现象。

• 检查路由注册与中间件顺序
  确认app.MapControllers()在UseAuthorization()之后（当前代码顺序正确），中间件顺序错误可能导致路由无法匹配。可在app.MapControllers()前添加代码，打印已注册的路由，验证控制器是否被正确发现：

  var endpointDataSource = app.Services.GetRequiredService<EndpointDataSource>();
  foreach (var endpoint in endpointDataSource.Endpoints)
  {
      if (endpoint is RouteEndpoint routeEndpoint)
      {
          Console.WriteLine($"已注册路由: {routeEndpoint.RoutePattern.RawText}");
      }
  }
  

  运行后查看控制台，若未出现api/companies路由，回到第一个排查点处理程序集加载问题。

• 排查依赖注入异常
  控制器构造函数依赖的IServiceManager及其链式依赖（如IRepositoryManager、RepositoryContext）若注册失败，可能导致程序启动异常但未直观报错。可在app.Run()前添加异常捕获，或检查开发环境日志：

  try
  {
      app.Run();
  }
  catch (Exception ex)
  {
      Console.WriteLine($"启动错误: {ex.Message}");
      throw;
  }
  

  同时确认appsettings.json中存在sqlconnection连接字符串，否则ConfigureSqlContext会导致DbContext注册失败，进而影响整个依赖链。

• 清理并重新生成项目
  编译缓存可能导致程序集加载异常，右键解决方案选择「清理」，再重新生成所有项目后运行调试。

内容的提问来源于stack exchange，提问作者Arpit Chinmay