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今天學習了 ExpandoObjecct類. 它可以實現在運行期間動態增加或刪除屬性方法或其它成員.豐富了我原來對 dynamic對象的使用.

Namespace: System.Dynamic Assembly: System.Linq.Expressions.dll

一. 實例化

dynamic sampleObject = new ExpandoObject(); 二. 增加屬性 , 方法 , 事件 //屬性:

sampleObject.test = "Dynamic Property";Console.WriteLine(sampleObject.test);Console.WriteLine(sampleObject.test.GetType());// This code example produces the following output:// Dynamic Property// System.String

//方法: 下例使用委託增加了一個方法

sampleObject.number = 10;sampleObject.Increment = (Action)(() => {
    sampleObject.number++; });// Before calling the Increment method.Console.WriteLine(sampleObject.number);sampleObject.Increment();// After calling the Increment method.Console.WriteLine(sampleObject.number);// This code example produces the following output:// 10// 11

//事件

class Program  {
         static void Main(string[] args)      {
             dynamic sampleObject = new ExpandoObject();          // Create a new event and initialize it with null.          sampleObject.sampleEvent = null;          // Add an event handler.          sampleObject.sampleEvent += new EventHandler(SampleHandler);          // Raise an event for testing purposes.          sampleObject.sampleEvent(sampleObject, new EventArgs());     }      // Event handler.      static void SampleHandler(object sender, EventArgs e)      {
             Console.WriteLine("SampleHandler for {0} event", sender);      }  }  // This code example produces the following output:  // SampleHandler for System.Dynamic.ExpandoObject event.

三. 作為參數

class Program{
       static void Main(string[] args)    {
           dynamic employee, manager;        employee = new ExpandoObject();        employee.Name = "John Smith";        employee.Age = 33;        manager = new ExpandoObject();        manager.Name = "Allison Brown";        manager.Age = 42;        manager.TeamSize = 10;        WritePerson(manager);        WritePerson(employee);    }    private static void WritePerson(dynamic person)    {
           Console.WriteLine("{0} is {1} years old.",                          person.Name, person.Age);        // The following statement causes an exception        // if you pass the employee object.        // Console.WriteLine("Manages {0} people", person.TeamSize);    }}// This code example produces the following output:// John Smith is 33 years old.// Allison Brown is 42 years old.

四. 枚舉或刪除成員

ExpandoObject 類實例化了IDictionary<String, Object>接口,因此我們可以對類成員進行枚舉,例如我們要枚舉成員或判斷是否包含某個成員.

dynamic employee = new ExpandoObject();employee.Name = "John Smith";employee.Age = 33;foreach (var property in (IDictionary
   
    )employee){
       Console.WriteLine(property.Key + ": " + property.Value);}// This code example produces the following output:// Name: John Smith// Age: 33
   

ExpandoObject 類本身沒有 delete 方法,我們可借轉化為 IDictionary 后再刪除.

dynamic employee = new ExpandoObject();employee.Name = "John Smith";((IDictionary
   
    )employee).Remove("Name");
   

五. 屬性變動通知事件

ExpandoObject實例了INotifyPropertyChanged 接口,所以當增加\刪除\修改了成員, 可以設置觸發事件.

// Add "using System.ComponentModel;" line// to the beginning of the file.class Program{
       static void Test()    {
           dynamic employee = new ExpandoObject();        ((INotifyPropertyChanged)employee).PropertyChanged +=            new PropertyChangedEventHandler(HandlePropertyChanges);        employee.Name = "John Smith";    }    private static void HandlePropertyChanges(        object sender, PropertyChangedEventArgs e)    {
           Console.WriteLine("{0} has changed.", e.PropertyName);    }}

其它詳細 可參考:

https://docs.microsoft.com/en-us/dotnet/api/system.dynamic.expandoobject?view=net-5.0

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