dynamic（翻译）

So I asked this guy, what's up with the dynamic keyword, and what type was it exactly? I mean, C# isn't dynamic, right? He says:

我问这个伙计，这dynamic关键字，是什么呢，它是什么类型呢?因为 我认为，c#不是动态类型，他应该有明确的意思和类型，我说的不对吗，但他说：

 

"Oh, well it's statically-typed as a dynamic type."

它是静态类型作为动态类型。

 

Then my brain exploded and began to leak out my ears. Honestly, though, it took a second. Here's a good example from some of Ander's slides:

我的思想开始爆发，实际上，这花费了我一些时间。这里是一个好的例子

 

Calculator calc = GetCalculator();

int sum = calc.Add(10, 20);

That's the creation of an object, invokation of a method, and the collection of a return value. This is the exact same code, as the "var" type is figured out at compile time.

创建一个对象，然后这个对象的方法，并获得方法的返回值。下面是一个同样的代码，但是稍微不同的是，用到了var(var定义的对象，必须在编译时能获得它的明确引用）

 

var calc = GetCalculator();

int sum = calc.Add(10, 20);

If you wanted to do the exact same thing, except with Reflection (like if it were some other class, maybe old-COM interop, or something where the compiler didn't know a priori that Add() was available, etc) you'd do this:

如果上面的对象不能在编译时指明的话，只能用反射（例如，一些其它的类，可能是old-com interop，或者其它的一些东西，导致编译器不能预先知道这个add方法，是有效的）

object calc = GetCalculator();

Type calcType = calc.GetType();

object res = calcType.InvokeMember("Add",

    BindingFlags.InvokeMethod, null,

    new object[] { 10, 20 });

int sum = Convert.ToInt32(res);

It's pretty horrible to look at, of course. If the object is some dynamic thing (from any number of sources), we can do this:

 

上面那段代码是多么的槽糕，如果一些东西是动态的，我们就可以做成下面这个样子的

 

dynamic calc = GetCalculator();

int sum = calc.Add(10, 20);

 

I'm told this is a dynamic expression that will be resolved at runtime.

Here's a C# program calling a method in a python (.py) file:

我告诉编译器，在运行时，解决这个对象问题。下面是利用dynamic调用python的方法。

1 2 3 4 5 6 7

ScriptRuntime py = Python.CreateRuntime(); dynamic random = py.UseFile("random.py");   //Make an array of numbers var items = Enumerable.Range(1, 7).ToArray();   random.shuffle(items);

原文链接：http://www.hanselman.com/blog/C4AndTheDynamicKeywordWhirlwindTourAroundNET4AndVisualStudio2010Beta1.aspx