C#筆記---動態類(Dynamic)應用

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           背景: 在Coding中有時候會遇到一些需要解析的資料,可是資料的欄位數量和名稱未統一，我們沒法定義實體類來對應。那麼我們就會想到通過C#的dynamic動態類來實現，如果大家注意的話一些ORM架構裡面貌似都有用到dynamic來實現一部分功能。

           一.Dynamic的基本應用

            1.1 通過.PropertyName來添加屬性,和JavaScript的對象差不多.不過對於我們所要解析的資料,我們事先也許根本不知道屬性名稱,所以用這種方法意義不大.

dynamic myObj = new ExpandoObject();myObj.Name = "Frank";Console.WriteLine(myObj.Name);

          二.Dynamic自訂屬性名稱.

           2.1: 繼承DynamicObject,裡面提供了各種方法,重寫後可以實現屬性的添加.

    public sealed class MyExtendsObject : DynamicObject    {        private readonly Dictionary<string, object> _properties;        public MyExtendsObject(Dictionary<string, object> properties)        {            _properties = properties;        }        public override IEnumerable<string> GetDynamicMemberNames()        {            return _properties.Keys;        }        public override bool TryGetMember(GetMemberBinder binder, out object result)        {            if (_properties.ContainsKey(binder.Name))            {                result = _properties[binder.Name];                return true;            }            else            {                result = null;                return false;            }        }        public override bool TrySetMember(SetMemberBinder binder, object value)        {            if (_properties.ContainsKey(binder.Name))            {                _properties[binder.Name] = value;                return true;            }            else            {                return false;            }        }    }

2.2 通過字典來添加屬性和賦值        

        public static void Main(string[] args)        {            dynamic myObj = new ExpandoObject();            Dictionary<string, object> dic = new Dictionary<string, object>()            {                {"Name","Frank"},                {"Age",23}            };            myObj = new MyExtendsObject(dic);            Console.WriteLine(myObj.Age); //23        }

           三.Dynamic解析XML.

            3.1 定義xml檔案:

<?xml version="1.0" encoding="utf-8" ?><Person>   <Name>Frank</Name>   <Age>23</Age>   <Address>TianFu SoftWarePark</Address></Person>

           3.2 繼承DynamicObject

 public sealed class MyExtensXMLObj : DynamicObject    {        private readonly XElement node;        public MyExtensXMLObj(XElement node)        {            this.node = node;        }        public override bool TrySetMember(SetMemberBinder binder, object value)        {            var elements = node.Elements().ToList();            var currentElement = elements.FirstOrDefault(x => x.Name == binder.Name);            if (currentElement != null)            {                currentElement.Value = value as string;                return true;            }            else            {                return false;            }        }        public override bool TryGetMember(GetMemberBinder binder, out object result)        {            var elements = node.Elements().ToList();            var currentElement = elements.FirstOrDefault(x => x.Name == binder.Name);            if (currentElement != null)            {                result = currentElement.Value;                return true;            }            else            {                result = null;                return false;            }        }    }

           3.3 結果輸出:

public static void Main(string[] args)        {            XElement root = XElement.Load(@"Test.xml");            dynamic personList = new MyExtensXMLObj(root);            Console.WriteLine(personList.Name); // Frank        }

        四. 繼承規則.

            1. 子類裡麵包含一個私人變數,用於儲存資料. 這暫且叫做Data;

            2.TryGetMember(GetMemberBinder binder, out object result) 方法實現對資料的擷取. binder.Name就是需要擷取的屬性的名稱,result 是擷取的屬性值. 通過binder.Name在Data中擷取到對應的屬性值,傳出到外面.(注意到了吧result是out參數)

            3.TrySetMember(SetMemberBinder binder, object value) 對存在的屬性進行賦值. 上面的Set方法中,我都判斷了binder.Name在data裡面是否存在。如果不存在就無法賦值。返回false,如果外面對不存在的屬性複製那麼將會報錯.

 

C#筆記---動態類(Dynamic)應用