WebApi2上进行依赖注入，在百度里能搜到的的完整解决方案的文章少之又少，缺胳膊断腿。

和MVC5依赖注入的不同之处，并且需要注意的地方，标记在注释当中。上Global代码：

namespace S2S.WebApi{    public class WebApiApplication : System.Web.HttpApplication    {        protected void Application_Start()        {            //----AutoFac  DI------            var builder = new ContainerBuilder();            SetupResolveRules(builder);            builder.RegisterApiControllers(Assembly.GetExecutingAssembly());               //RegisterApiControllers方法            var container = builder.Build();            HttpConfiguration config = GlobalConfiguration.Configuration;//注意此处HttpConfiguration类的 config对象，一定不要new,要从GlobalConfiguration获取            config.DependencyResolver = (new AutofacWebApiDependencyResolver(container));      //注意此处与MVC依赖注入不同            //---------------------------------------------------------            AreaRegistration.RegisterAllAreas();            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);            RouteConfig.RegisterRoutes(RouteTable.Routes);            BundleConfig.RegisterBundles(BundleTable.Bundles);                        AreaRegistration.RegisterAllAreas();            GlobalConfiguration.Configure(WebApiConfig.Register);            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);            RouteConfig.RegisterRoutes(RouteTable.Routes);            BundleConfig.RegisterBundles(BundleTable.Bundles);        }          /// 
       ///  AutoFac        /// 
        ///         private static void SetupResolveRules(ContainerBuilder builder)        {            var assembly = Assembly.Load("s2s.BLL");   //根据程序集名称加载程序集            builder.RegisterAssemblyTypes(assembly).SingleInstance();//每次都返回同一个实例            builder.RegisterAssemblyTypes(assembly).Where(t => t.Name.EndsWith("Service")).AsImplementedInterfaces();        }    }}

　也没有太多需要解释的地方，Controller中还是构造器注入。开发中已经亲测有效。　

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