原文:WebAPI增加Area以支持无限层级同名Controller
微软的WebAPI默认实现逻辑
默认实现中不支持同名Controller，否则在访问时会报HttpError，在网上找到了各种路由自实现，如
给ASP.net Web API的Controller分类
搭建MVC及WebAPI项目框架时碰到的问题集合
在上述地址的帮助下，根据需求，重新编写了AreaHttpControllerSelector，路由原理与上述地址大同小异，均是通过路由匹配拼接FullName，然后匹配最接近的ApiController，而所谓的最接近，就是指如果根据拼接的Name获取到了多个匹配项，则获取命名空间节点数最少的那个ApiController，以保证在多次注册路由规则时，能够按照从繁到简的方式匹配出相应的Controller（需要注意的是AreaHttpControllerSelector是以controller作为结束分割点的），举例如下
假定注册了以下路由匹配规则（controller、action均为WebAPI的路由占用字符）
config.Routes.MapHttpRoute(
name: "DefaultAreaApi",
routeTemplate: "api/{area}/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{action}/{id}",
defaults: new { id = RouteParameter.Optional }
);
在Controller目录下存在多层同名且不同层级的Controller，如：
Controller/Area/SameController，对应的命名空间为Controller.Area.SameController
Controller/SameController，对应的命名空间为Controller.SameController
通过api/Area/Same/Get将匹配到Controller/Area/SameController
通过api/Same/Get将匹配到Controller/SameController
相比于参考网址，重新编写的AreaHttpControllerSelector可以支持无限层级的区域，只要命名空间支持，比如
"api/{area1}/{area1}/{area2}/{area3}/{controller}/{action}/{id}"
以下是具体的AreaHttpControllerSelector代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web;
using System.Web.Http.Dispatcher;
using System.Net.Http;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Net; namespace WebAPI
{
/// <summary>
/// Represents a area System.Web.Http.Dispatcher.IHttpControllerSelector instance
/// </summary>
public class AreaHttpControllerSelector : DefaultHttpControllerSelector
{
private readonly HttpConfiguration _configuration;
/// <summary>
/// Lazy 当前程序集中包含的所有IHttpController反射集合，TKey为小写的Controller
/// </summary>
private readonly Lazy<ILookup<string, Type>> _apiControllerTypes;
private ILookup<string, Type> ApiControllerTypes
{
get
{
return this._apiControllerTypes.Value;
}
}
/// <summary>
/// Initializes a new instance of the AreaHttpControllerSelector class
/// </summary>
/// <param name="configuration"></param>
public AreaHttpControllerSelector(HttpConfiguration configuration)
: base(configuration)
{
this._configuration = configuration;
this._apiControllerTypes = new Lazy<ILookup<string, Type>>(this.GetApiControllerTypes);
}
/// <summary>
/// 获取当前程序集中 IHttpController反射集合
/// </summary>
/// <returns></returns>
private ILookup<string, Type> GetApiControllerTypes()
{
IAssembliesResolver assembliesResolver = this._configuration.Services.GetAssembliesResolver();
return this._configuration.Services.GetHttpControllerTypeResolver()
.GetControllerTypes(assembliesResolver)
.ToLookup(t => t.Name.ToLower().Substring(0, t.Name.Length - DefaultHttpControllerSelector.ControllerSuffix.Length), t => t);
}
/// <summary>
/// Selects a System.Web.Http.Controllers.HttpControllerDescriptor for the given System.Net.Http.HttpRequestMessage.
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
{
HttpControllerDescriptor des = null;
string controllerName = this.GetControllerName(request);
if (!string.IsNullOrWhiteSpace(controllerName))
{
var groups = this.ApiControllerTypes[controllerName.ToLower()];
if (groups != null && groups.Any())
{
string endString;
var routeDic = request.GetRouteData().Values;//存在controllerName的话必定能取到IHttpRouteData
if (routeDic.Count > 1)
{
StringBuilder tmp = new StringBuilder();
foreach (var key in routeDic.Keys)
{
tmp.Append('.');
tmp.Append(routeDic[key]);
if (key.Equals(DefaultHttpControllerSelector.ControllerSuffix, StringComparison.CurrentCultureIgnoreCase))
{//如果是control，则代表命名空间结束
break;
}
}
tmp.Append(DefaultHttpControllerSelector.ControllerSuffix);
endString = tmp.ToString();
}
else
{
endString = string.Format(".{0}{1}", controllerName, DefaultHttpControllerSelector.ControllerSuffix);
}
//取NameSpace节点数最少的Type
var type = groups.Where(t => t.FullName.EndsWith(endString, StringComparison.CurrentCultureIgnoreCase))
.OrderBy(t => t.FullName.Count(s => s == '.')).FirstOrDefault();//默认返回命名空间节点数最少的第一项
if (type != null)
{
des = new HttpControllerDescriptor(this._configuration, controllerName, type);
}
}
}
if (des == null)
{
throw new HttpResponseException(request.CreateErrorResponse(HttpStatusCode.NotFound,
string.Format("No route providing a controller name was found to match request URI '{0}'", request.RequestUri)));
}
return des;
}
}
}
而用法就是在Global文件的Application_Start方法中替换注册
GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerSelector),
new AreaHttpControllerSelector(
GlobalConfiguration.Configuration));
