名詞解釋

DLR: dynamic language runtime.

refer to this article: http://msdn.microsoft.com/en-us/vstudio/ff800651.aspx

下面是一個簡單的實現，會動態的創建需要的屬性：

      class Program

    {

        static void Main(string[] args)

        {

            dynamic dynamicProperties = new MyDynamicObject();



            try

            {

                Console.WriteLine(dynamicProperties.Marker);

            }

            catch (Microsoft.CSharp.RuntimeBinder.RuntimeBinderException)

            {

                Console.WriteLine("There is no such a property.");

            }



            dynamicProperties.Date = DateTime.Now;

            dynamicProperties.Name = "Bill Wagner";

            dynamicProperties.Title = "Effective C#";

            dynamicProperties.Content = "Building a dynamic dictionary";



            Console.WriteLine(dynamicProperties);

            Console.ReadLine();

        }

    }



    class MyDynamicObject : DynamicObject

    {

        private Dictionary<string, object> storage = new Dictionary<string, object>();

        public override bool TryGetMember(GetMemberBinder binder, out object result)

        {

            if (storage.ContainsKey(binder.Name))

            {

                result = storage[binder.Name];

                return true;

            }

            result = null;

            return false;

        }



        public override bool TrySetMember(SetMemberBinder binder, object value)

        {

            string key = binder.Name;

            if (storage.ContainsKey(key))

                storage[key] = value;

            else

                storage.Add(key, value);



            return true;

        }



        public override string ToString()

        {

            var sb = new StringBuilder();

            foreach (var item in storage)

                sb.AppendLine(string.Format("{0}:\t{1}", item.Key, item.Value));



            return sb.ToString();

        }

    }


    

更比較通用的是ExpandoObject類，可以在運行是動態的添加或刪除成員，包括屬性，事件等等。

例如，

1. 添加新屬性：

dynamic sampleObject = new ExpandoObject();

sampleObject.test = "Dynamic Property" ;
Console.WriteLine(sampleObject.test);
Console.WriteLine(sampleObject.test.GetType());

2.?添加事件(lambda或event)：

// 2.1 add lambda expression

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);

// 2.2 add event

// Create a new event and initialize it with null. must declare it first.
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);
}

3. 作為參數傳遞

dynamic employee = new ExpandoObject();
employee.Name = "John Smith" ;
employee.Age = 33;

WritePerson(employee);

private static void WritePerson( dynamic person)

{
??????? Console.WriteLine( "{0} is {1} years old." , person.Name, person.Age);

}
4. 枚舉成員：

因為該類實現了IDictionary<string, object>接口，所以可以枚舉它的成員。

dynamic employee = new ExpandoObject();
employee.Name = "John Smith";
employee.Age = 33;

foreach (var property in (IDictionary<String, Object>)employee)
{
??? Console.WriteLine(property.Key + ": " + property.Value);
}
// This code example produces the following output:
// Name: John Smith
// Age: 33

// 刪除某個成員
dynamic employee = new ExpandoObject();
employee.Name = "John Smith";
((IDictionary<String, Object>)employee).Remove("Name");

5. 通知機制
// 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);
??? }
}

?

?

Implementing Dynamic Interfaces