According to the Gang of Four definitions, the Command Design Pattern is used to encapsulate a request as an object (i.e., a command) and ship it to an invoker, who does not recognise how to serve the request but plays a movement in the usage of the encased command.

The Command Design Pattern is a Behavioral Design Pattern that converts a request into a standalone object containing all of the request's contents. This transformation enables you to parameterize methods with various requests, postpone or queue request execution, and permit undoable operations. It is handy in situations where you need to send requests without knowing anything about the operation or the receiver.

Example to Understand the Command Design Pattern:

Let us illustrate the preceding definition with an example. First, the Command Object contains the Request (i.e., what to do). Second, it includes the Receiver Object Reference. The receiver object is simply the object that will handle the request. Third, the command object includes the Execute method. The Execute method will call the receiver object method, which will process the request.

According to the Command Design Pattern, the Command Object will be handed to the Invoker Object. The Invoker Object does not understand how to process the request. The Invoker will call the Execute method of the Command Object. The Execute method of the command object will be renamed the Receiver Object Method. The Receiver Object Method will take the appropriate actions to process the request. 

Real-Time Example of the Command Design Pattern:

To help you understand the Command Design Pattern, I used the example of a restaurant. In a restaurant, the waiter will be present. What the Waiter will do is take the customer's order. The customer will inform the waiter of his or her preferred cuisine. The waiter will write it down on a checklist. The Waiter then provides the checklist to the Cook. The cook prepares the meals and returns it to the waiter, who returns it to the purchaser.
 

In this situation, the Customer is the Client. The Command is the customer's order, which specifies the type of meals they want. The Waiter is the Invoker. The waiter does not recognize the way to prepare dinner. So the Waiter forwards the request to the Receiver, i.e., the Cook, who prepares the food and returns it to the Waiter, who then returns it to the client.

How to Implement the Command Design Pattern in C#?

The Command layout pattern encapsulates a request as an item, permitting customers to parameterize customers with numerous requests, queue requests, log requests, and help undoable movements. It entails separating objects that issue commands from objects that carry out the directives. Here's a quick overview of the Command Design Pattern:

• Command: This is an interface for carrying out an activity.
• ConcreteCommand: This class extends the Command interface by invoking the appropriate operation(s) on the Receiver object.
• Receiver: This class understands how to carry out the activities connected with a request. Any class may act as a receiver.
• Invoker: This class asks the command to execute the request.
• Client: The client makes a concrete command object and sets its receiver.

When to Use Command Design Pattern in C#?

Parameterizing Objects with Operations: When you need to parameterize objects with an action to do, the Command pattern can encapsulate the action as an object, allowing for dynamic assignment and execution.

Decoupling the Sender and Receiver: If you wish to separate the object that makes the request (sender) from the objects that carry it out (receivers). This split improves modularity and flexibility in the code.

Queuing, Logging, and Undoable Operations: In situations when you need to queue activities, log modifications, or support undoable actions. Commands can be stored, replayed, or reversed as needed, giving you complete control over functionality.

Callback capability is used in applications to execute commands at a later time.

Supporting Undo/Redo in User Interfaces: In GUI programs, actions taken by the user can be reversed (undo) or reapplied. Each action can be represented as a command that can be undone or redone.

Transactional Behavior: When implementing transactional behavior, many operations must be handled as a single atomic operation. The Command pattern can help you implement such requirements.

Extending Applications: In cases where an application needs to be expanded with additional commands without affecting the present code. New command classes can be introduced to provide new capabilities.