Chapter 2: Creating Versatile Types

This chapter is all about making your own objects as useful and versatile as possible. In many cases, this means implementing the standard interfaces that .NET provides or simply overriding base class methods.

Prevent Inheritance

Scenario/Problem: You want to prevent users of your class from inheriting from it.

Solution: Mark the class as sealed.

sealed class MyClass
{
    ...
}

Structs are inherently sealed.

Prevent Overriding of a Single Method

Scenario/Problem: You don't want to ban inheritance on your type, but you do want to prevent certain methods or properties from being overridden.

Solution: Put sealed as part of the method or property definition.

class ParentClass
{
    public virtual void MyFunc() { }
}
class ChildClass : ParentClass
{
    //seal base class function into this class
    public sealed override void MyFunc() { }
}
class GrandChildClass : ChildClass
{
    //yields compile error
    public override void MyFunc() { }
}