C# Classes and Objects Flashcards

Questions and Answers

Classes are to Objects as...

Classes create instances

Classes define types and Objects are instances of a type (correct)

Objects define the state

Objects are classes

What do classes define?

State

Behavior

Access

All of the above (correct)

What are Objects?

Instances of a class (correct)

A type of class

Abstract blueprints

Static members

What are constructors?

Special methods to create objects. Signup and view all the answers

What do reference types create?

Classes create reference types. Signup and view all the answers

What concepts does Object-Oriented Programming (OOP) include?

All of the above Signup and view all the answers

What is inheritance?

Creating classes to extend other classes. Signup and view all the answers

What are access modifiers?

Keywords to declare the accessibility of a type or member. Signup and view all the answers

What does the keyword 'public' mean?

No access restrictions Signup and view all the answers

What does the keyword 'protected' indicate?

Access limited to the class and derived classes Signup and view all the answers

What does the keyword 'internal' signify?

Access limited to the current assembly Signup and view all the answers

What does 'protected internal' mean?

Access limited to the current assembly and derived types. Signup and view all the answers

What does the keyword 'private' restrict?

Access limited to the class. Signup and view all the answers

What is an abstract class?

A class designed as a base class that cannot be instantiated. Signup and view all the answers

What does the virtual keyword do?

Creates a virtual member that can be overridden in a derived class. Signup and view all the answers

What are static classes?

Classes that can only have static members and cannot be instantiated. Signup and view all the answers

What are sealed classes?

Classes that cannot be inherited. Signup and view all the answers

What are partial classes?

Classes that can span multiple files within the same project. Signup and view all the answers

Which features provide performance, convenience, and extensibility?

All of the above Signup and view all the answers

Study Notes

Classes and Objects

Classes define data types, while Objects are individual instances of those types.
Each Object maintains unique states but shares the same behavior defined by its Class.

Class Characteristics

Classes consist of State (attributes), Behavior (methods), and Access (visibility).

Object Instances

Multiple Objects can be created from a single Class.
Each Object instance can have a different state, but they exhibit identical behaviors.

Constructors

Constructors are special methods designed for initializing Objects.
They can set default values and may be overloaded using different argument signatures.

Reference Types

Classes are reference types, meaning that the Object resides on the heap.
Variables hold references pointing to the Object's memory location.

Object Oriented Programming (OOP)

C# follows OOP principles such as Inheritance, Encapsulation, and Polymorphism.

Inheritance

Inheritance allows a Class to extend another Class, inheriting its properties and behaviors.
All Classes in C# inherit from System.Object by default.

Access Modifiers

Access modifiers control the accessibility of Classes or their members within the code.

Public Keyword

The "public" keyword indicates no restrictions on access to a Class or Member.

Protected Keyword

The "protected" keyword restricts access to Members, allowing access only within the Class itself and derived Classes.

Internal Keyword

The "internal" keyword limits access to Classes or Members within the current assembly only.

Protected Internal Keyword

The "protected internal" keyword allows access within the current assembly and through derived types.

Private Keyword

The "private" keyword restricts access to Members solely within the defining Class.

Abstract Classes and Members

The "abstract" keyword can be applied to Classes and Members, which cannot be instantiated directly.
Abstract Classes serve as base classes, requiring concrete implementations of abstract Members in derived Classes.

Virtual Members

The "virtual" keyword allows a Class member to be overridden in derived Classes.
Members are non-virtual by default and virtual dispatch occurs based on the runtime type of the Object.

Static Classes

Static members cannot be accessed through instance Objects; they belong to the Class itself.
Only static members can exist within a Static Class, which cannot be instantiated.

Sealed Classes

Sealed Classes cannot be inherited, ensuring they remain unmodified and optimizing performance and security.

Partial Classes

Partial Classes allow definitions to be split across multiple files but within the same project.
Partial methods serve as extensibility points and are eliminated at compile time if left unimplemented.

Performance Enhancement Features

Static, Sealed, and Partial Classes improve performance, convenience, and extensibility in C#.

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Description

Test your knowledge of classes and objects in C# with these flashcards. Understand the relationship between classes and objects, and learn about constructors and their roles in object-oriented programming. This quiz will help reinforce key concepts related to defining types and creating instances in C#.