ASP.NET MVC 5 实战：从路由到过滤器

参与了公司第一个 MVC 5 项目后，我把一些核心机制重新梳理了一遍。Web Forms 时代那种”控件拖放”的开发方式虽然快，但对 HTTP 的控制力很弱，测试也困难。MVC 5 让我第一次真正理解了请求处理流程，这篇文章记录下我的理解。

1. 路由系统

MVC 5 的路由在 RouteConfig.cs 中配置：

public class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

        // 带约束的路由
        routes.MapRoute(
            name: "ProductDetail",
            url: "products/{id}",
            defaults: new { controller = "Products", action = "Detail" },
            constraints: new { id = @"\d+" } // 只匹配数字 ID
        );

        // 默认路由
        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );
    }
}

Attribute Routing（推荐）：

MVC 5 支持直接在 Action 上声明路由，更直观：

[RoutePrefix("api/users")]
public class UsersController : Controller
{
    [Route("")]
    public ActionResult Index() { ... }

    [Route("{id:int}")]
    public ActionResult Detail(int id) { ... }

    [Route("{id:int}/orders")]
    public ActionResult Orders(int id) { ... }
}

2. Model Binding

MVC 5 会自动将请求数据绑定到 Action 参数：

// 简单类型：从路由、QueryString、Form 按顺序查找
public ActionResult Search(string keyword, int page = 1, int pageSize = 10)
{
    // GET /search?keyword=mvc&page=2
}

// 复杂类型：递归绑定所有公共属性
public ActionResult Create(CreateUserDto dto)
{
    if (!ModelState.IsValid)
    {
        return View(dto);
    }
    // ...
}

public class CreateUserDto
{
    [Required]
    [StringLength(50)]
    public string Name { get; set; }

    [Required]
    [EmailAddress]
    public string Email { get; set; }

    [Range(18, 100)]
    public int Age { get; set; }
}

自定义 Model Binder：

// 将逗号分隔的字符串绑定为 List<int>
public class IntListModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext,
                            ModelBindingContext bindingContext)
    {
        var value = bindingContext.ValueProvider
                                  .GetValue(bindingContext.ModelName)?.AttemptedValue;
        if (string.IsNullOrEmpty(value)) return new List<int>();

        return value.Split(',')
                    .Select(s => int.TryParse(s.Trim(), out int n) ? n : (int?)null)
                    .Where(n => n.HasValue)
                    .Select(n => n.Value)
                    .ToList();
    }
}

// 注册
ModelBinders.Binders.Add(typeof(List<int>), new IntListModelBinder());

3. 过滤器管道

MVC 5 的过滤器按顺序执行，共 4 种类型：

1	`Authorization → Action → Result → Exception`

自定义授权过滤器：

public class RequirePermissionAttribute : AuthorizeAttribute
{
    private readonly string _permission;

    public RequirePermissionAttribute(string permission)
    {
        _permission = permission;
    }

    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        var user = httpContext.User;
        if (!user.Identity.IsAuthenticated) return false;

        // 从用户 Claims 中检查权限
        return user.HasClaim("permission", _permission);
    }

    protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
    {
        if (filterContext.HttpContext.Request.IsAjaxRequest())
        {
            filterContext.Result = new JsonResult
            {
                Data = new { success = false, message = "无权限" },
                JsonRequestBehavior = JsonRequestBehavior.AllowGet
            };
        }
        else
        {
            base.HandleUnauthorizedRequest(filterContext);
        }
    }
}

// 使用
[RequirePermission("user:write")]
public ActionResult Create(CreateUserDto dto) { ... }

Action 过滤器（日志记录）：

public class ActionLogAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var action = filterContext.ActionDescriptor.ActionName;
        var controller = filterContext.ActionDescriptor.ControllerDescriptor.ControllerName;
        var user = filterContext.HttpContext.User.Identity.Name;
        Log.Info($"[{user}] {controller}.{action} 开始执行");
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        if (filterContext.Exception != null)
        {
            Log.Error("Action 执行异常", filterContext.Exception);
        }
    }
}

全局异常处理：

public class GlobalExceptionFilter : HandleErrorAttribute
{
    public override void OnException(ExceptionContext filterContext)
    {
        if (filterContext.ExceptionHandled) return;

        Log.Error("未处理异常", filterContext.Exception);

        if (filterContext.HttpContext.Request.IsAjaxRequest())
        {
            filterContext.Result = new JsonResult
            {
                Data = new { success = false, message = "服务器内部错误" }
            };
        }
        else
        {
            filterContext.Result = new ViewResult { ViewName = "Error" };
        }

        filterContext.ExceptionHandled = true;
        filterContext.HttpContext.Response.StatusCode = 500;
    }
}

// 全局注册
filters.Add(new GlobalExceptionFilter());

4. 依赖注入集成

MVC 5 本身不内置 DI，需要通过 IDependencyResolver 集成第三方容器（以 Autofac 为例）：

public class AutofacDependencyResolver : IDependencyResolver
{
    private readonly IContainer _container;

    public AutofacDependencyResolver(IContainer container)
    {
        _container = container;
    }

    public object GetService(Type serviceType)
    {
        return _container.IsRegistered(serviceType)
            ? _container.Resolve(serviceType)
            : null;
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        var type = typeof(IEnumerable<>).MakeGenericType(serviceType);
        return _container.IsRegistered(type)
            ? (IEnumerable<object>)_container.Resolve(type)
            : Enumerable.Empty<object>();
    }
}

// Global.asax 中配置
var builder = new ContainerBuilder();
builder.RegisterControllers(Assembly.GetExecutingAssembly());
builder.RegisterType<UserService>().As<IUserService>().InstancePerRequest();
var container = builder.Build();
DependencyResolver.SetResolver(new AutofacDependencyResolver(container));

5. 单元测试

MVC 的架构让 Controller 测试变得容易：

[TestClass]
public class UsersControllerTests
{
    private Mock<IUserService> _mockService;
    private UsersController _controller;

    [TestInitialize]
    public void Setup()
    {
        _mockService = new Mock<IUserService>();
        _controller = new UsersController(_mockService.Object);
    }

    [TestMethod]
    public void Index_ReturnsViewWithUsers()
    {
        // Arrange
        var users = new List<User> { new User { Name = "Alice" } };
        _mockService.Setup(s => s.GetAll()).Returns(users);

        // Act
        var result = _controller.Index() as ViewResult;

        // Assert
        Assert.IsNotNull(result);
        var model = result.Model as List<User>;
        Assert.AreEqual(1, model.Count);
    }
}

总结

ASP.NET MVC 5 相较于 Web Forms 的核心优势在于：

可测试性：Controller 与 HTTP 解耦，业务逻辑可单独测试
对 HTML/HTTP 的完全控制：没有 ViewState 和隐藏字段干扰
路由灵活：Attribute Routing 让 URL 设计更语义化
过滤器管道：横切关注点（日志、权限、异常）以声明式方式实现

从 Web Forms 迁过来需要转变思维：MVC 要求你理解 HTTP 请求-响应模型，而不是把它抽象成”事件驱动”。这个转变一旦完成，代码质量和可维护性都会显著提升。