Specifies that a declared element is incomplete or lacks implementation.
- You cannot create an instance of an abstract class.
- Combined modifiers
- You cannot combine Abstract with other modifiers such as Shared and Override in the same declaration.
- When you derive a non-abstract class from an abstract class, the new class must provide implementations of all abstract methods and properties that it inherited.
- Declaration contexts
- You can declare abstract methods and properties only within an abstract class.