早期绑定、动态绑定、后期绑定
这里所说的绑定并不是指对一个控件的数据绑定。这种绑定是指与类之间建立某种联系的过程,比如在CMD程序中要调用另外一个程序集中的类的方法:在ConsoleApplication程序中:
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相反,在Class1调用Class2 的方法时候并没有引用Class2那么这个过程就是“后期绑定”了。也就是说Class2对于Class1是完全未知的情况下被调用的。针对上面的程序我们这样修改:
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Console.WriteLine(methodInfo.Invoke(obj,null));
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其实这里的绑定的定义并不是C#最先提出的,早在VB6.0时代,就有“早期绑定”和“后期绑定”之分,只不过在VB6.0中的定义要狭隘的多:只有当变量被定义为Object 或 Variant 类型时候才属于“后期绑定”。同样很容易发现在解释执行的语言中没有“早期绑定”,而C#提供的“后期绑定”研究意味着使用C#开发一门解释型的语言也是很easy的。
最后我们来看看这两者分别用在什么地方。就大多数程序来说,一般都应该使用“早期绑定”,因为很显然它的性能要高一些。而“后期绑定”应该用在特殊的地方,比如在程序中可以调用插件,这必然是需要“后期绑定”的。在破解上“反射注册机”的编写也需要“后期绑定”,编写解释性语言也需要“后期绑定”。因此可见“后期绑定”在对程序集的处理上更加的灵活。