.Net 4.0 ExpandoObject 使用（上）_转

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。

1.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。

posted on 2010-08-28 17:50 一粒沙阅读(1321) 评论(0) 编辑收藏举报