本篇文章中就ExpandoObject的基本使用进行一些demo。我们几乎都知道dynamic特性是.net 4.0中一个主要的新特性，而ExpandoObject正是这样的一个动态的类型。ExpandoObject允许我们在实例化之后在运行时进行成员的增加、删除。下面我们来看下基本的使用：
Adding Members
1)实例化
如果需要延迟绑定的话，我们需要用dynamic来定义ExpandpObject的实例化变量，关于dynamic的使用，估计大家都很清楚了。
dynamic obj = new ExpandoObject();
2）增加属性成员
[TestMethod]
public void ExpandoObjectTest()
{
dynamic employee = new ExpandoObject();
employee.FirstName = "Henry";
employee.LastName = "Cui";
employee.Age = 23;
Console.WriteLine("Employee's name :{0} age:{1}",
employee.FirstName + employee.LastName,
employee.Age);
}
测试的结果：
3）增加Method
在增加方法的时候，先把成员表现成delegate,先看一个没有参数的无返回值的方法：
[TestMethod]
public void ExpandoObjectTest()
{
dynamic employee = new ExpandoObject();
employee.FirstName = "Henry";
employee.LastName = "Cui";
employee.Age = 23;
employee.SayHello = (Action)(() =>
{
Console.WriteLine("{0} say \"Hello\" at {1}",
employee.FirstName+" "+employee.LastName,
DateTime.UtcNow.ToString());
});
employee.SayHello();
}
在上面的示例中我们将SayHello定义成委托Action类型，并给了默认方法。
下面来看一个有参数、有返回值的：
[TestMethod]
public void ExpandoObjectTest()
{
dynamic employee = new ExpandoObject();
employee.FirstName = "Henry";
employee.LastName = "Cui";
employee.Age = 23;
employee.SayHello = (Action)(() =>
{
Console.WriteLine("{0} say \"Hello\" at {1}",
employee.FirstName+" "+employee.LastName,
DateTime.UtcNow.ToString());
});
employee.GetSalary = (Func<int, decimal>)((month) =>
{
if (month > 8)
return 5000;
return 4000;
});
Console.WriteLine("The employee's october salary is :${0}",
employee.GetSalary(10).ToString());
}
测试结果：
上面的例子中是段很简单的逻辑就是超过8月份的时候就返回$5000，呵呵。
4）增加Event
在实例中我们定义一个请假事件，员工请假就会上报给经理：
[TestClass]
public class DynamicTest
{
[TestMethod]
public void ExpandoObjectTest()
{
dynamic employee = new ExpandoObject();
employee.FirstName = "Henry";
employee.LastName = "Cui";
employee.Age = 23;
employee.SayHello = (Action)(() =>
{
Console.WriteLine("{0} say \"Hello\" at {1}",
employee.FirstName+" "+employee.LastName,
DateTime.UtcNow.ToString());
});
employee.GetSalary = (Func<int, decimal>)((month) =>
{
if (month > 8)
return 5000;
return 4000;
});
employee.AskForLeaveEvent = null;
employee.AskForLeaveEvent += new EventHandler(OnEmployeeLeave);
employee.AskForLeaveEvent(employee,new EventArgs());
}
public void OnEmployeeLeave(object sender, EventArgs e)
{
dynamic em = (dynamic)sender;
Console.WriteLine("Report Manager:{0} is asking for leave", em.FirstName + " " + em.LastName);
}
我们看下运行的结果：
Remove Members
其实ExpandoObject继承了IDictionary<String, Object>的接口,所以我们枚举出在运行时增加的那些成员.
1)枚举出已经存在的成员
我们就来枚举出刚才在employee中增加的成员们：
foreach (var pro in (IDictionary<string, Object>)employee)
{
Console.WriteLine(pro.Key+" "+pro.Value);
}
我们可以看到测试结果：
2）移除成员
其实我们还是利用了ExpandoObject实现了IDictionary接口去实现的，我们移除掉AskForLeaveEvent事件：
((IDictionary<string, object>)employee).Remove("AskForLeaveEvent");
foreach (var pro in (IDictionary<string, Object>)employee)
{
Console.WriteLine(pro.Key+" "+pro.Value);
}
我们看看运行的结果：
我们可以看到AskForLeaveEvent被移除了。
总结
本文中主要介绍了ExpandoObject的基本使用，我们发现真的有点动态语言的风味，写过javascript的人感觉会太别爽，呵呵。下文中会就ExpandoObject的原理以及一些扩展就行一些说明。
