O'Reilly C# 5.0 in a Nutshell, 5th Edition 9781449320102 Manual Do Utilizador
Códigos do produto
9781449320102
languages such as C++ and Eiffel, C# does not support multiple inheritance of
classes).
classes).
Properties, methods, and events
In the pure object-oriented paradigm, all functions are methods (this is the case
in Smalltalk). In C#, methods are only one kind of function member, which also
includes properties and events (there are others, too). Properties are function
members that encapsulate a piece of an object’s state, such as a button’s color
or a label’s text. Events are function members that simplify acting on object
state changes.
in Smalltalk). In C#, methods are only one kind of function member, which also
includes properties and events (there are others, too). Properties are function
members that encapsulate a piece of an object’s state, such as a button’s color
or a label’s text. Events are function members that simplify acting on object
state changes.
Type Safety
C# is primarily a type-safe language, meaning that instances of types can interact
only through protocols they define, thereby ensuring each type’s internal consis-
tency. For instance, C# prevents you from interacting with a string type as though
it were an integer type.
only through protocols they define, thereby ensuring each type’s internal consis-
tency. For instance, C# prevents you from interacting with a string type as though
it were an integer type.
More specifically, C# supports static typing, meaning that the language enforces
type safety at compile time. This is in addition to type safety being enforced at
runtime.
type safety at compile time. This is in addition to type safety being enforced at
runtime.
Static typing eliminates a large class of errors before a program is even run. It shifts
the burden away from runtime unit tests onto the compiler to verify that all the types
in a program fit together correctly. This makes large programs much easier to man-
age, more predictable, and more robust. Furthermore, static typing allows tools such
as IntelliSense in Visual Studio to help you write a program, since it knows for a
given variable what type it is, and hence what methods you can call on that variable.
the burden away from runtime unit tests onto the compiler to verify that all the types
in a program fit together correctly. This makes large programs much easier to man-
age, more predictable, and more robust. Furthermore, static typing allows tools such
as IntelliSense in Visual Studio to help you write a program, since it knows for a
given variable what type it is, and hence what methods you can call on that variable.
C# also allows parts of your code to be dynamically typed via
the
the
dynamic
keyword (introduced in C# 4). However, C# re-
mains a predominantly statically typed language.
C# is also called a strongly typed language because its type rules (whether enforced
statically or at runtime) are very strict. For instance, you cannot call a function that’s
designed to accept an integer with a floating-point number, unless you first explic-
itly convert the floating-point number to an integer. This helps prevent mistakes.
statically or at runtime) are very strict. For instance, you cannot call a function that’s
designed to accept an integer with a floating-point number, unless you first explic-
itly convert the floating-point number to an integer. This helps prevent mistakes.
Strong typing also plays a role in enabling C# code to run in a sandbox—an envi-
ronment where every aspect of security is controlled by the host. In a sandbox, it is
important that you cannot arbitrarily corrupt the state of an object by bypassing its
type rules.
ronment where every aspect of security is controlled by the host. In a sandbox, it is
important that you cannot arbitrarily corrupt the state of an object by bypassing its
type rules.
Memory Management
C# relies on the runtime to perform automatic memory management. The Common
Language Runtime has a garbage collector that executes as part of your program,
reclaiming memory for objects that are no longer referenced. This frees programmers
Language Runtime has a garbage collector that executes as part of your program,
reclaiming memory for objects that are no longer referenced. This frees programmers
2 | Chapter 1:
Introducing C# and the .NET Framework