.Net 4.0 ExpandoObject 使用(上)
2010-06-20 10:59 Henry Cui 阅读(4355) 评论(13) 编辑 收藏 举报本篇文章中就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。