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Chapter ‎18   Unsafe code

the call F(1) invokes the F declared in Inner because all outer occurrences of F are hidden by the inner declaration. For the same reason, the call F("Hello") results in a compile-time error.

3.7.1.2 Hiding through inheritance

Name hiding through inheritance occurs when classes or structs redeclare names that were inherited from base classes. This type of name hiding takes one of the following forms:

A constant, field, property, event, or type introduced in a class or struct hides all base class members with the same name.

A method introduced in a class or struct hides all non-method base class members with the same name, and all base class methods with the same signature (method name and parameter count, modifiers, and types).

An indexer introduced in a class or struct hides all base class indexers with the same signature (parameter count and types).

The rules governing operator declarations (§‎10.9) make it impossible for a derived class to declare an operator with the same signature as an operator in a base class. Thus, operators never hide one another.

Contrary to hiding a name from an outer scope, hiding an accessible name from an inherited scope causes a warning to be reported. In the example

class Base { public void F() {} }

class Derived: Base { public void F() {}// Warning, hiding an inherited name }

the declaration of F in Derived causes a warning to be reported. Hiding an inherited name is specifically not an error, since that would preclude separate evolution of base classes. For example, the above situation might have come about because a later version of Base introduced an F method that wasn’t present in an earlier version of the class. Had the above situation been an error, then any change made to a base class in a separately versioned class library could potentially cause derived classes to become invalid.

The warning caused by hiding an inherited name can be eliminated through use of the new modifier:

class Base { public void F() {} }

class Derived: Base { new public void F() {} }

The new modifier indicates that the F in Derived is “new”, and that it is indeed intended to hide the inherited member.

A declaration of a new member hides an inherited member only within the scope of the new member.

class Base { public static void F() {} }

Copyright Microsoft Corporation 1999-2003. All Rights Reserved.67

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