什么是ExpandoObject的真正好处是什么？ [英] What are the true benefits of ExpandoObject?

问题描述

的<一个href="http://msdn.microsoft.com/en-us/library/system.dynamic.expandoobject%28VS.100%29.aspx">ExpandoObject类被添加到.NET 4中，您可以随意设置属性到对象在运行时。

The ExpandoObject class being added to .NET 4 allows you to arbitrarily set properties onto an object at runtime.

有什么优势，这种过度使用<一个href="http://msdn.microsoft.com/en-us/library/xfhwa508.aspx"><$c$c>Dictionary<string,object>,还是真的连一个哈希表？据我所知，这只不过是一个哈希表，您可以使用稍微更简洁的语法进行访问。

Are there any advantages to this over using a Dictionary<string,object>, or really even a Hashtable? As far as I can tell, this is nothing but a hash table that you can access with slightly more succinct syntax.

例如，为什么是这样的：

For example, why is this:

dynamic obj = new ExpandoObject();
obj.MyInt = 3;
obj.MyString = "Foo";
Console.WriteLine(obj.MyString);

真的好，还是完全不同的，比：

Really better, or substantially different, than:

var obj = new Dictionary<string, object>();
obj["MyInt"] = 3;
obj["MyString"] = "Foo";

Console.WriteLine(obj["MyString"]);

什么真正的优点是通过使用ExpandoObject而不是只使用一个任意字典式上涨，比不是很明显，您使用的类型将是在运行时确定等。

What real advantages are gained by using ExpandoObject instead of just using an arbitrary dictionary type, other than not being obvious that you're using a type that's going to be determined at runtime.

推荐答案

自从我写了MSDN文章你指的是，我想我必须回答这个问题。

Since I wrote the MSDN article you are referring to, I guess I have to answer this one.

首先，我预计这个问题，这就是为什么我写了一篇博客文章，显示了或多或少的实际使用情况进行ExpandoObject：<一href="http://blogs.msdn.com/csharpfaq/archive/2009/10/01/dynamic-in-c-4-0-introducing-the-expandoobject.aspx">Dynamic在C＃4.0：介绍ExpandoObject 。

First, I anticipated this question and that's why I wrote a blog post that shows a more or less real use case for ExpandoObject: Dynamic in C# 4.0: Introducing the ExpandoObject.

不久，ExpandoObject可以帮助您创建复杂的分层对象。例如，假设你有一个字典中的字典：

Shortly, ExpandoObject can help you create complex hierarchical objects. For example, imagine that you have a dictionary within a dictionary:

Dictionary<String, object> dict = new Dictionary<string, object>();
Dictionary<String, object> address = new Dictionary<string,object>();
dict["Address"] = address;
address["State"] = "WA";
Console.WriteLine(((Dictionary<string,object>)dict["Address"])["State"]);

更深的层次，在丑陋的code。随着ExpandoObject它保持优雅和可读性。

The deeper is the hierarchy, the uglier is the code. With ExpandoObject it stays elegant and readable.

dynamic expando = new ExpandoObject();
expando.Address = new ExpandoObject();
expando.Address.State = "WA";
Console.WriteLine(expando.Address.State);

其次，因为它已经指出，ExpandoObject实现INotifyPropertyChanged接口，为您提供了更多的控制权比一本字典的属性。

Second, as it was already pointed out, ExpandoObject implements INotifyPropertyChanged interface which gives you more control over properties than a dictionary.

最后，你可以添加事件ExpandoObject喜欢这里：

Finally, you can add events to ExpandoObject like here:

class Program
{

   static void Main(string[] args)
   {
       dynamic d = new ExpandoObject();

       // Initialize the event to null (meaning no handlers)
       d.MyEvent = null;

       // Add some handlers
       d.MyEvent += new EventHandler(OnMyEvent);
       d.MyEvent += new EventHandler(OnMyEvent2);

       // Fire the event
       EventHandler e = d.MyEvent;

       if (e != null)
       {
           e(d, new EventArgs());
       }

       // We could also fire it with...
       //      d.MyEvent(d, new EventArgs());

       // ...if we knew for sure that the event is non-null.
   }

   static void OnMyEvent(object sender, EventArgs e)
   {
       Console.WriteLine("OnMyEvent fired by: {0}", sender);
   }

   static void OnMyEvent2(object sender, EventArgs e)
   {
       Console.WriteLine("OnMyEvent2 fired by: {0}", sender);
   }
}

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