C # sealed keywords

SealedModifiers can be applied to classes, instance methods, and attributes.
The class modified by sealed is a sealed class, which cannot be inherited.
The method modified by sealed is the sealing method. The sealing method will override the methods in the base class, but it cannot be further rewritten in any derived class. When applied to methods or attributes, the sealed modifier must always be used with override.

Use the sealed modifier in the class declaration to prevent this class from being inherited. For example:

Sealed class sealedclass {public int X; Public int y ;}

When sealed modifies a class, the class cannot be abstract, that is, it cannot be both an abstract class and a sealed class.
In addition,Note that the structure (struct) is implicitly sealed. Therefore, they cannot be inherited.