ASP. NET learning notes (13) sealed, new, virtual, abstract, and override

1. The sealed sealing class cannot be inherited. The sealing method can override the methods in the base class, but cannot be overwritten in any subclass.
It must always be used with override when applied to methods and attributes.

2. new indicates that the member inherited from the base class is hidden. If new is not used, a warning is displayed.

3. virtual Methods and attributes are called virtual members. By default, methods are non-virtual and non-virtual methods cannot be rewritten.
1. virtual cannot be used for static attributes.
2. Rewrite the virtual inheritance attribute in the subclass by using override

4. abstract indicates that this class can only be the base class of other classes.

Abstract class:
1. It cannot be instantiated.
2. Non-Abstract subclasses must include all abstract methods of the base class and the implementation of the abstract accessors.

Abstract method:
1. the abstract method is an implicit virtual method.
2. Only abstract methods can be used in abstract classes.
3. the Declaration does not provide implementation, usually ended with a semicolon, for example, public abstract void MyMethod ();
4. abstract methods cannot be modified using static or virtual

5. override is used to override abstract and virtual modified members in the base class.

By: dxh_0829