State Design Pattern in C#

The State Design Pattern is a behavioral design pattern that allows an object to alter its behavior when its internal state changes. This pattern is particularly useful for implementing state machines and ensuring that the object’s behavior remains manageable and modular.

This pattern is useful when an object needs to go through several states, and its behavior differs for each state. Instead of having conditional statements throughout a class to handle state-specific behaviors, the State Design Pattern delegates this responsibility to individual state classes.

Components of State Desgin Pattern

1. Context: This is the class that contains an instance of a state and delegates state-specific behavior to the current state object.
2. State: An interface that encapsulates the behavior associated with a particular state of the Context.
3. Concrete States: Classes that implement the State interface, each representing a specific state and defining its behavior.

Chain of Responsibility Pattern in C#

The Chain of Responsibility pattern is a behavioral design pattern that allows a group of objects to handle a request sequentially, each potentially handling the request or passing it on to the next object in the chain until the request is handled or reaches the end of the chain.

In simple words, we can say that the chain of responsibility design pattern creates a chain of receiver objects for a given request. In this design pattern, normally, each receiver contains a reference to the next receiver. If one receiver cannot handle the request, it passes the same request to the next receiver, and so on. In this case, one receiver can handle the request in the chain, or one or more receivers can handle the request.

Components of Chain of Resposibility Pattern

1. Handler Interface (or Abstract Class): This defines a common interface for all handlers. It typically includes a method for handling requests and a reference to the next handler in the chain.
2. Concrete Handlers: These are the actual handlers in the chain. Each handler implements the Handler interface and contains logic to handle requests. If it can't handle a request, it passes it to the next handler in the chain.
3. Client: This initiates the request and sends it to the first handler in the chain.

Mediator Design Pattern in C#

The Mediator Design Pattern is a behavioral design pattern that promotes loose coupling between objects by encapsulating how they interact. It centralizes complex communication logic between multiple objects into a mediator object, thus reducing direct dependencies between them. This promotes easier maintenance and scalability of the system.

The Mediator Design Pattern restricts direct communications between the objects and forces them to collaborate only via a mediator object. This pattern is used to centralize complex communications and control between related objects in a system. The Mediator object acts as the communication center for all objects. That means when an object needs to communicate with another object, it does not call the other object directly. Instead, it calls the mediator object, and it is the responsibility of the mediator object to route the message to the destination object.

Components of Mediator Design Pattern

1. Mediator: Defines an interface for communication between colleague objects.
2. Colleague: It is an abstract class, and Concrete Colleague classes will implement this abstract class.
3. ConcreteMediator: Implements the mediator interface, coordinating communication between colleague objects.
4. ConcreteColleague: Implements the colleague interface and communicates with other colleagues through the mediator.

Template Method Design Pattern in C#

The Template Method Design Pattern is a behavioral design pattern that defines the skeleton of an algorithm in the superclass but lets subclasses override specific steps of the algorithm without changing its structure. It allows reusing common behavior across multiple classes while still allowing customization where necessary.

Components of Template Method Design Pattern

• Abstract Class: This class defines the template method, which is the skeleton of the algorithm. It consists of several abstract methods that subclasses must implement.
• Concrete Classes: These classes inherit from the abstract class and provide implementations for the abstract methods.

Command Design Pattern in C#

The Command Design Pattern is a behavioral design pattern that encapsulates a request as an object, thereby allowing parameterization of clients with queues, requests, and operations. This pattern decouples sender and receiver of a request based on a command, which helps in invoking the right method at the right time without knowing the actual implementation details.

Components of Command Design Pattern

1. Command: Defines an interface for executing an operation.
2. Concrete Command: Implements the Command interface and binds a receiver with an action. It defines a binding between the action and the receiver.
3. Invoker: Requests the command to execute the operation.
4. Receiver: Knows how to perform the operation.