“是"- 类型运算符 [英] "is" - operator for Type

问题描述

我使用is"运算符来查找某个类:

I use the "is" operator to find a certain class:

for(int i=0; i<screens.Count; i++){
  if(screen is ScreenBase){
    //do something...
  }
}

这很有效，尤其是当它找到从 ScreenBase 继承的任何类而不是从 ScreenBase 继承的基类时.

This works fine especially as it finds any class that inherits from the ScreenBase but not the base classes from ScreenBase.

当我只知道类型并且不想实例化类时，我想这样做:

I would like to do the same when I know only the Type and don't want to instantiate the class:

Type screenType = GetType(line);
if (screenType is ScreenBase)

但是这个比较会产生一个警告，因为它将与Type"类进行比较.

But this comparsion produces a warning as it will compare to the "Type" class.

我知道的唯一替代方法是与 ==typeof 进行比较，但这只会测试确切的类型而不是继承的类型.有没有办法获得类似于is"运算符的类似行为，但对于 Type-class 描述的类型?

The only alternative I know would be to compare with ==typeof but this would test only for the exact type and not the inherited ones. Is there a way to get a similar behaviour like the "is" operator but for the type described by the Type-class?

推荐答案

如果您想具体了解它是否源自类型，请使用 Type.IsSubclassOf().这不适用于接口.

If you want to know specifically if it derives from the type, use Type.IsSubclassOf(). This will not work for interfaces.

Type screenType = GetType(line);
if (screenType.IsSubclassOf(typeof(ScreenBase)))
{
    // do stuff...
}

否则，如果您想知道该类型是否可以分配给某个类型的变量，请使用 Type.IsAssignableFrom().这将适用于接口.

Otherwise if you want to know if the type could be assigned to a variable of a certain type, use Type.IsAssignableFrom(). This will work for interfaces.

Type screenType = GetType(line);
if (typeof(ScreenBase).IsAssignableFrom(screenType)) // note the usage is reversed
{
    // do stuff...
}

请注意，您不一定需要类型对象来确定这一点，您可以使用 Type.IsInstanceOfType().它的行为或多或少类似于 IsAssignableFrom().

Do note that you don't necessarily need a type object to determine this, you can do this with an instance of the object using Type.IsInstanceOfType(). It will behave more or less like IsAssignableFrom().

if (typeof(ScreenBase).IsInstanceOfType(line)) // note the usage is reversed
{
    // do stuff...
}

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