反射

1.通过反射创建对象 方法1

        public static IMessageReceiver CreateInstance(WeixinMessage weixinMessage)
        {
            IMessageReceiver result = null;
            MessageTypeAttribute messageTypeAttribute = null;
            EventTypeAttribute eventTypeAttribute = null;
            string weixinMessageTypeEnumTitle = EnumHelper.GetEnumTitle(weixinMessage.Type);
            foreach (Type type in MessageReceiverTypeList)
            {

                messageTypeAttribute = AssemblyHelper.GetTypeAttribute<MessageTypeAttribute>(type);
                if (messageTypeAttribute!=null&&messageTypeAttribute.Name == weixinMessageTypeEnumTitle)
                {
                    if (messageTypeAttribute.Name == "Event")
                    {
                        string eventType = weixinMessage.Body.Event.Value.ToLower();
                        eventTypeAttribute = AssemblyHelper.GetTypeAttribute<EventTypeAttribute>(type);
                        if(eventTypeAttribute.Name==eventType)
                        {
                            result = (IMessageReceiver)Activator.CreateInstance(type, true);//根据类型创建实例
                            break;
                        }
                    }
                    else
                    {
                        result = (IMessageReceiver)Activator.CreateInstance(type, true);//根据类型创建实例
                         break;
                    }
                    
                }

            }
            if (result != null)
            {
                result.Receive(weixinMessage);
                return result;
            }
            else
            {
                throw new Exception("not support this message type");
            }
        }

2.通过反射创建对象 方法2

        public static MessageBehavior Analysis(IMessageReceiver messageReceiver)
        {
           
            MessageBehaviorAttribute messageBehaviorAttribute = null;
            var messageReceiverType = messageReceiver.GetType();
            var attrs = AssemblyHelper.GetAllTypeAttributes(messageReceiver.GetType());
            foreach(var attr in attrs)
            {
                if (attr.GetType() == typeof(MessageBehaviorAttribute))
                {
                    messageBehaviorAttribute = (MessageBehaviorAttribute)attr;
                    break;
                }
            }

            Type messageBehaviorType = MessageBehaviorTypeList.Where(u => u.Name == messageBehaviorAttribute.Name).FirstOrDefault();
            if(messageBehaviorType!=null)
            {
                object[] parameters = new object[1];
                parameters[0] = messageReceiver;
                Assembly assembly = Assembly.GetExecutingAssembly();
                MessageBehavior behavior = (MessageBehavior)assembly.CreateInstance(messageBehaviorType.FullName, true, System.Reflection.BindingFlags.Default, null, parameters, null, null);// 

                return behavior;
            }
            return null;
        }

 3.得到入口程序集，兼容Web和Winform

        public static Assembly GetEntryAssembly()
        {
            var entryAssembly = Assembly.GetEntryAssembly();
            if (entryAssembly != null)
                return entryAssembly;
            
            if (System.Web.HttpContext.Current == null ||
                System.Web.HttpContext.Current.ApplicationInstance == null)
                return Assembly.GetExecutingAssembly();

            var type = System.Web.HttpContext.Current.ApplicationInstance.GetType();
            while (type != null && type.Namespace == "ASP")
            {
                type = type.BaseType;
            }

            return type == null ? null : type.Assembly;
        }
       

4.得到当前应用程序的根目录

        public static string GetBaseDirectory()
        {
            var baseDirectory = AppDomain.CurrentDomain.SetupInformation.PrivateBinPath;

            if (AppDomain.CurrentDomain.SetupInformation.PrivateBinPath == null)
                baseDirectory = AppDomain.CurrentDomain.BaseDirectory;

            return baseDirectory;
        }

5.扫描程序集找到继承了某基类的所有子类　　

     public static List<Type> FindTypeByInheritType(Type inheritType, string searchpattern = "*.dll")
        {
            var result = new List<Type>();
            Type attr = inheritType;

            string domain = GetBaseDirectory();
            string[] dllFiles = Directory.GetFiles(domain, searchpattern, SearchOption.TopDirectoryOnly);

            foreach (string dllFileName in dllFiles)
            {
                foreach (Type type in Assembly.LoadFrom(dllFileName).GetLoadableTypes())
                {
                    if (type.BaseType == inheritType)
                    {
                        result.Add(type);
                    }
                }
            }

            return result;
        }

6.扫描程序集找到某接口的所有子类

        public static List<Type> FindAllTypeByInterface<T>(string searchpattern = "*.dll") where T : class
        {
            var result = new List<Type>();
            var interfaceType = typeof(T);

            string domain = GetBaseDirectory();
            string[] dllFiles = Directory.GetFiles(domain, searchpattern, SearchOption.TopDirectoryOnly);

            foreach (string dllFileName in dllFiles)
            {
                foreach (Type type in Assembly.LoadFrom(dllFileName).GetLoadableTypes())
                {
                    if (type.GetInterface(interfaceType.Name) != null && !type.IsInterface && !type.IsAbstract)
                    {
                        result.Add(type);
                    }

                }
            }

            return result;
        }