ExpandoObject :
动态的增删一个对象的属性，在低层库（比如ORM）中非常实用。
因为ExpandoObject实现了IDictionay<string, object>接口，常见的一种使用方法是，把expando转成dictionary，动态添加属性名和值[key,value]，expando就达到了动态属性的目的。  演示样例代码（using System.Dynamic）：

dynamic expando = new ExpandoObject();

	expando.A = "a";

	expando.B = 1;

	// A,a

	// B,1

	IDictionary<string, object> dict = expando as IDictionary<string, object>;

	foreach(var e in dict){

		Console.WriteLine(e.Key + ","+ e.Value);

	}

	dict.Add("C", "c");

	// c

	Console.WriteLine(expando.C);

DynamicObject 类：
当须要track一个对象的属性被get或set时。这个类是非常好的候选。 （通常出如今AOP的设计中，假设不打算使用AOP框架比如POSTSHARP的话）。演示样例代码：

void Main()

{

	dynamic obj = new MyDynaObject();

	obj.A = "a";

	obj.B = 1;

	var a = obj.A;

	// should print :

//	tring to set member : A, with value : a

//	tring to set member : B, with value : 1

//	tring to get member : a

}

public class MyDynaObject : DynamicObject

{

    // The inner dictionary.

    Dictionary<string, object> dictionary

        = new Dictionary<string, object>();

    // This property returns the number of elements

    // in the inner dictionary.

    public int Count

    {

        get

        {

            return dictionary.Count;

        }

    }

    // If you try to get a value of a property

    // not defined in the class, this method is called.

    public override bool TryGetMember(

        GetMemberBinder binder, out object result)

    {

        // Converting the property name to lowercase

        // so that property names become case-insensitive.

        string name = binder.Name.ToLower();

		Console.WriteLine("tring to get member : {0}", name);

        // If the property name is found in a dictionary,

        // set the result parameter to the property value and return true.

        // Otherwise, return false.

        return dictionary.TryGetValue(name, out result);

    }

    // If you try to set a value of a property that is

    // not defined in the class, this method is called.

    public override bool TrySetMember(

        SetMemberBinder binder, object value)

    {

        // Converting the property name to lowercase

        // so that property names become case-insensitive.

        dictionary[binder.Name.ToLower()] = value;

		Console.WriteLine("tring to set member : {0}, with value : {1}", binder.Name, value);

        // You can always add a value to a dictionary,

        // so this method always returns true.

        return true;

    }

}

// Define other methods and classes