为什么我们可以创建位图实例 [英] why we could create instance of bitmap

问题描述

位图是一个密封的类.为什么我可以创建实例.??而没有图形?

Bitmap is a seald class.why i can create instance.????while with The graphics are not??

推荐答案

密封并不意味着您不能使用它:这意味着您不能从中继承.

您可以创建任何未标记为静态的类的实例:由于C#没有全局变量的概念，因此无法实例化的类将不可用.

为什么位图是密封类?可能是为了阻止人们添加它，并期望这些添加在位图文件中起作用.鉴于位图文件的格式是固定的，这将是有道理的.

另一方面，Graphics对象不是密封的:您可以继承它并对其进行增强.如果所需的draw方法不存在，那么至少可以添加功能.

Sealed does not mean you cannot use it: it means that you cannot inherit from it.

You can create an instance of any class that is not marked static: Since C# has no concept of global variables, a class that you could not instantiate would not be usable.

Why is Bitmap a sealed class? Probably to stop people adding to it and expecting the additions to work in the bitmap file. Given that the format of a Bitmap file is fixed, that would make sense.

The Graphics object on the other hand is not sealed: you can inherit from it and enhance it. That at least allows for facilities to be added if the required draw method does not exist.

阅读一些文档.
sealed =不能从该class继承；可以实例化它，当然，如果它具有public构造函数.
Graphics class没有public构造函数.这就是为什么您不能以这种方式实例化它的原因.但是，您可以通过其他方式(static方法，e.Graphics的e.Graphics ...)创建它的实例

Read some documentation.
sealed = cannot inherit from that class; can instantiate it, of course if it has a public constructor.
Graphics class does not have a public constructor. That''s why you can''t instantiate it that way. You can however create an instance of it through other means (static methods, e.Graphics from events...)

不能继承<<密封的类，并且不能是抽象的.
因此，绝对有可能创建一个新实例.

干杯

A sealed class cannot be inherited and it cannot be abstract.
So it definitely possible create a new instance.

Cheers

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