IsAssignableFrom和＆QUOT使用;是＆QUOT;关键字在C＃

问题描述

而努力学习Unity,我不断看到下面的code在MVC覆盖 GetControllerInstance ：

 如果（！typeof运算（一个IController）.IsAssignableFrom（controllerType））{...}
 

这似乎对我pretty的基本写作方法错综复杂

 如果（controllerType是一个IController）{...}
 

我AP preciate有之间的细微差别是和 IsAssignableFrom ，即 IsAssignableFrom 不包括投转换，但我在努力了解实际情况下这种差别的含义。

当它是imporantant选择 IsAssignableFrom 在是？这将使在什么区别 GetControllerExample ？

 如果（！typeof运算（一个IController）.IsAssignableFrom（controllerType））
      抛出新的ArgumentException（...）;
返回_container.Resolve（controllerType）作为一个IController;
 

解决方案

这是不一样的。

 如果（controllerType是一个IController）
 

将总是的计算结果为假，因为 controllerType 总是键入和键入从来都不是一个IController 。

的是运算符是用来检查是否一个例如是给定类型兼容。

该IsAssignableFrom方法用于检查键入是否与给定类型兼容。

While trying to learn Unity, I keep seeing the following code for overriding GetControllerInstance in MVC:

if(!typeof(IController).IsAssignableFrom(controllerType)) { ... }

this seems to me a pretty convoluted way of basically writing

if(controllerType is IController) { ... }

I appreciate there are subtle differences between is and IsAssignableFrom, ie IsAssignableFrom doesn't include cast conversions, but I'm struggling to understand the implication of this difference in practical scenarios.

When is it imporantant to choose IsAssignableFrom over is? What difference would it make in the GetControllerExample?

if (!typeof(IController).IsAssignableFrom(controllerType))
      throw new ArgumentException(...);
return _container.Resolve(controllerType) as IController;

解决方案

It's not the same.

if(controllerType is IController)

would always evaluate to false since controllerType is always a Type, and a Type is never an IController.

The is operator is used to check whether an instance is compatible to a given type.

The IsAssignableFrom method is used to check whether a Type is compatible with a given type.

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