HttpRouteBuilder - 它去了哪里以及为什么？

我将 Web API 2 的 nuget 包从 RC1 升级到了 5.0.0，然后傻眼地发现原来可以访问的 HttpRouteBuilder 变成了内部的。除此之外，不再有以 HttpRouteBuilder 作为参数的 HttpConfiguration.MapHttpAttributeRoutes 的重载。为什么？

我正在使用它，它解决了我项目中的一个主要问题。我该用什么来代替？

背景： 我正在编写一个使用 Web API 2 属性路由的服务器。我实现了一个从 HttpRouteBuilder 继承的类，以便我可以向每个 URI 注入几个额外的路径段。例如，如果默认路由构建器最终创建了一条路由//我的服务器/用户/更新，我的路线构建器会将该路线修改为//myserver/{实例}/用户/更新。我希望自动完成此操作，这样我就不必将其添加到数百个 HttpGet、HttpPost 等属性中。那么现在我该如何处理这个重大变化呢？

这种内部因素也破坏了我正在做的事情。

A 2013 年 8 月 21 日进行的更改 http://aspnetwebstack.codeplex.com/SourceControl/changeset/2c71056731959debf3e6d3e764270b1fc51956aa对此 api 进行了更改以修复这个问题 http://aspnetwebstack.codeplex.com/workitem/1229。根据该问题，删除功能的唯一原因是使 Web Api 更接近 MVC 的 api。我认为这并不是一个特别好的理由。

为了解决我的问题，我实施了自定义IHttpActionSelector源自ApiControllerActionSelector。我希望这不会是我的最终解决方案，因为对于一个简单的事情来说，代码确实太多了。这种方法也应该适用于您的问题。

在我的项目中，每个路由都需要根据在哪个程序集中找到它进行修改。在下面的简化代码中，每个路由都带有前缀/Api（在控制器之前RoutePrefixAttribute如果存在）。

实际上IHttpActionSelector:

public class PrefixWithApiControllerActionSelector : WrappingApiControllerActionSelector {
    protected override HttpActionDescriptor WrapHttpActionDescriptor(HttpActionDescriptor actionDescriptor) {
        if (actionDescriptor is ReflectedHttpActionDescriptor)
            return new PrefixWithApiReflectedHttpActionDescriptor((ReflectedHttpActionDescriptor)actionDescriptor);
        return actionDescriptor;
    }
}

public abstract class WrappingApiControllerActionSelector : ApiControllerActionSelector {
    protected abstract HttpActionDescriptor WrapHttpActionDescriptor(HttpActionDescriptor actionDescriptor);

    public override ILookup<string, HttpActionDescriptor> GetActionMapping(HttpControllerDescriptor controllerDescriptor) {
        return base.GetActionMapping(controllerDescriptor).SelectMany(grouping => {
            return grouping.Select(actionDescriptor => new KeyValuePair<string, HttpActionDescriptor>(grouping.Key, WrapHttpActionDescriptor(actionDescriptor)));
        }).ToLookup(_ => _.Key, _ => _.Value);
    }
}

改变路线的部分：

public class PrefixWithApiHttpRouteInfoProvider : WrappedHttpRouteInfoProvider {
    public PrefixWithApiHttpRouteInfoProvider(IHttpRouteInfoProvider infoProvider, HttpControllerDescriptor controllerDescriptor) : base(infoProvider, controllerDescriptor) { }

    public override string Template {
        get {
            var parts = new List<string>();
            parts.Add("Api");

            var prefix = ControllerDescriptor.GetCustomAttributes<RoutePrefixAttribute>().FirstOrDefault();
            if (prefix != null && !string.IsNullOrEmpty(prefix.Prefix)) {
                parts.Add(prefix.Prefix);
            }

            if (!string.IsNullOrEmpty(InfoProvider.Template)) {
                parts.Add(InfoProvider.Template);
            }

            var route = "~/" + string.Join("/", parts);
            if (route.Length > 2 && route.EndsWith("/", StringComparison.Ordinal)) {
                route = route.Substring(0, route.Length - 1);
            }
            return route;
        }
    }
}

public abstract class WrappedHttpRouteInfoProvider : IHttpRouteInfoProvider {
    private readonly IHttpRouteInfoProvider _infoProvider;
    private readonly HttpControllerDescriptor _controllerDescriptor;

    protected WrappedHttpRouteInfoProvider(IHttpRouteInfoProvider infoProvider, HttpControllerDescriptor controllerDescriptor) {
        _infoProvider = infoProvider;
        _controllerDescriptor = controllerDescriptor;
    }

    public virtual string Name {
        get { return InfoProvider.Name; }
    }

    public virtual string Template {
        get { return _infoProvider.Template; }
    }

    public virtual int Order {
        get { return InfoProvider.Order; }
    }

    protected HttpControllerDescriptor ControllerDescriptor {
        get { return _controllerDescriptor; }
    }

    protected IHttpRouteInfoProvider InfoProvider {
        get { return _infoProvider; }
    }
}

胶水：

public class PrefixWithApiReflectedHttpActionDescriptor : WrappedReflectedHttpActionDescriptor {
    public PrefixWithApiReflectedHttpActionDescriptor(ReflectedHttpActionDescriptor descriptor) : base(descriptor) {}

    public override Collection<T> GetCustomAttributes<T>(bool inherit) {
        if (typeof(T) == typeof(IHttpRouteInfoProvider)) {
            var attributes = Descriptor.GetCustomAttributes<T>(inherit).Cast<IHttpRouteInfoProvider>().Select(_ => new PrefixWithApiHttpRouteInfoProvider(_, Descriptor.ControllerDescriptor));
            return new Collection<T>(attributes.Cast<T>().ToList());
        }
        return Descriptor.GetCustomAttributes<T>(inherit);
    }

    public override Collection<T> GetCustomAttributes<T>() {
        if (typeof(T) == typeof(IHttpRouteInfoProvider)) {
            var attributes = Descriptor.GetCustomAttributes<T>().Cast<IHttpRouteInfoProvider>().Select(_ => new PrefixWithApiHttpRouteInfoProvider(_, Descriptor.ControllerDescriptor));
            return new Collection<T>(attributes.Cast<T>().ToList());
        }
        return Descriptor.GetCustomAttributes<T>();
    }
}

public abstract class WrappedReflectedHttpActionDescriptor : ReflectedHttpActionDescriptor {
    private readonly ReflectedHttpActionDescriptor _descriptor;

    protected WrappedReflectedHttpActionDescriptor(ReflectedHttpActionDescriptor descriptor) : base(descriptor.ControllerDescriptor, descriptor.MethodInfo) {
        _descriptor = descriptor;
    }

    public override HttpActionBinding ActionBinding {
        get { return Descriptor.ActionBinding; }
        set { Descriptor.ActionBinding = value; }
    }

    public override Collection<T> GetCustomAttributes<T>(bool inherit) {
        return Descriptor.GetCustomAttributes<T>(inherit);
    }

    public override Collection<T> GetCustomAttributes<T>() {
        return Descriptor.GetCustomAttributes<T>();
    }

    public override Collection<System.Web.Http.Filters.FilterInfo> GetFilterPipeline() {
        return Descriptor.GetFilterPipeline();
    }

    public override Collection<System.Web.Http.Filters.IFilter> GetFilters() {
        return Descriptor.GetFilters();
    }

    public override System.Collections.Concurrent.ConcurrentDictionary<object, object> Properties {
        get { return Descriptor.Properties; }
    }

    public override IActionResultConverter ResultConverter {
        get { return Descriptor.ResultConverter; }
    }

    public override Collection<HttpMethod> SupportedHttpMethods {
        get { return Descriptor.SupportedHttpMethods; }
    }

    public override Collection<HttpParameterDescriptor> GetParameters() {
        return Descriptor.GetParameters();
    }

    public override Task<object> ExecuteAsync(HttpControllerContext controllerContext, IDictionary<string, object> arguments, CancellationToken cancellationToken) {
        return Descriptor.ExecuteAsync(controllerContext, arguments, cancellationToken);
    }

    public override string ActionName {
        get { return Descriptor.ActionName; }
    }

    public override Type ReturnType {
        get { return Descriptor.ReturnType; }
    }

    protected ReflectedHttpActionDescriptor Descriptor {
        get { return _descriptor; }
    }
}

要使用此功能只需替换IHttpActionSelector服务与PrefixWithApiControllerActionSelector在配置中。

如果您找到更干净的做事方式，请发布您的解决方案！