Implementing Dynamic Interfaces
名词解释
DLR: dynamic language runtime.
refer to this article:http://msdn.microsoft.com/en-us/vstudio/ff800651.aspx
下面是一个简单的实现，会动态的创建需要的属性：
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();
}
}
更比较通用的是ExpandoObject类，可以在运行是动态的添加或删除成员，包括属性，事件等等。
例如，
1. 添加新属性：
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. 作为参数传递
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. 枚举成员：
因为该类实现了IDictionary<string, object>接口，所以可以枚举它的成员。
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
// 删除某个成员
dynamic employee = new ExpandoObject();
employee.Name = "John Smith";
((IDictionary<String, Object>)employee).Remove("Name");
5. 通知机制
// 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);
}
}