在WebApi 中使用AutoFac

参考文档

https://www.cnblogs.com/htsboke/p/10956807.html

https://www.cnblogs.com/lenmom/p/8510572.html
https://www.cnblogs.com/yaopengfei/p/9479268.html

在WebApi项目中使用AutoFac，结构如下：

首先在Api项目当中引用AutoFac包，如下图所示：

仓储类：

    public interface IUsersRepository
    {
        int GetUserIsExists(UsersEntity criteria);

    }


    public class UsersRepository : IUsersRepository
    {
        Logger log = LogManager.GetLogger("UsersRepository");

        /// <summary>
        /// 获取用户是否存在
        /// </summary>
        /// <param name="criteria"></param>
        /// <returns></returns>
        public int GetUserIsExists(UsersEntity criteria)
        {
            string sql = "。。。。";
            try
            {
                 //查询sql代码，此处省略。。。。             
               }
            catch (Exception ex)
            {
                log.Fatal(ex, "获取用户是否存在异常：{0}，SQL：{1}", ex.Message, sql);
                return 0;
            }
        }
    }

服务类：

    //接口   
       public interface IUsersService
    {
        int GetUserIsExists(UsersEntity criteria);

    }

    //实现类
    public class UsersService : IUsersService
    {
        private readonly IUsersRepository _usersrepository;     
        public UsersService(IUsersRepository usersrepository)    //通过构造函数注入
        {
            _usersrepository = usersrepository;
        }

        /// <summary>
        /// 获取用户是否存在
        /// </summary>
        /// <param name="criteria"></param>
        /// <returns></returns>
        public int GetUserIsExists(UsersEntity criteria)
        {
            return _usersrepository.GetUserIsExists(criteria);
        }
    }

在Api接口项目中创建一个AutoFac工具类：AutofacUtil.cs   

    public class AutofacUtil
    {
        private static IContainer _container;

        public static void ConfigureContainer()
        {
            #region AutoFac IOC容器

            var builder = new ContainerBuilder();

            try
            {
                //builder.RegisterControllers(Assembly.GetCallingAssembly());  //注册mvc控制器  需要引用package Autofac.Mvc

                //builder.RegisterApiControllers(Assembly.GetExecutingAssembly()).PropertiesAutowired();  //支持Api控制器属性注入
                builder.RegisterApiControllers(Assembly.GetCallingAssembly());  //注册所有api控制器  构造函数注入  需要引用package Autofac.WebApi

                //注册程序集
                #region Service
                var assemblysServices = Assembly.Load("WebApi.Service");
                builder.RegisterAssemblyTypes(assemblysServices)
                .AsImplementedInterfaces()
                .InstancePerDependency();
                #endregion
                
                #region Repository
                var assemblysRepository = Assembly.Load("WebApi.Repository");
                builder.RegisterAssemblyTypes(assemblysRepository)
                .AsImplementedInterfaces()
                .InstancePerDependency();
                #endregion

                _container = builder.Build();   //创建依赖注入


                //设置MVC依赖注入
                //DependencyResolver.SetResolver(new AutofacDependencyResolver(_container));

                //设置WebApi依赖注入
                GlobalConfiguration.Configuration.DependencyResolver = new AutofacWebApiDependencyResolver(_container);
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message + "
" + ex.InnerException);
            }
            #endregion
        }

        /// <summary>
        /// 从Autofac容器获取对象
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static T GetFromFac<T>()
        {
            return _container.Resolve<T>();
        }

    }

在 Global.asax.cs 全局中注册一下：

  public class WebApiApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            GlobalConfiguration.Configure(WebApiConfig.Register);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            //AutoFac 注册
            AutofacUtil.ConfigureContainer();

        }
    }

最后在接口中使用：

    public class UsersController : ApiController
    {
        private readonly IUsersService _usersService;
        public UsersController(IUsersService usersService)    //使用构造函数注入
        {
            _usersService = usersService;
        }


        /// <summary>
        /// 获取用户是否存在
        /// </summary>
        /// <param name="username"></param>
        /// <param name="password"></param>
        /// <returns></returns>
        [HttpPost]
        public IHttpActionResult GetUserIsExists(string username, string password)
        {
            //验证是否存在当前用户
            var obModel = new UsersEntity()
            {
                Username = username,
                Password = Encryption.MD5(password)
            };
            var getresult = _usersService.GetUserIsExists(obModel);

            return Json(new { isexists = getresult > 0 });
        }


    }

测试结果：

最后：如果出现 未将对象引用的实例 的错误，检查一下是否引用相应的dll程序集了。