C# Design Pattern Interview Questions

Design Patterns are the solutions to the Software Design problems which are common. The commonly occurring problems can be resolved by applying the Design Patterns. C# is an object-oriented language which is used to develop applications along with the .NET framework. The Design Patterns are the best practices to find out the solutions for the complex known problems in the architectural or design challenges of the software designs. These design solutions for the problems were obtained by making numerous trial and error methods by many software developers over the due course to obtain efficient solutions to the general problems. The C# programming language is efficient in terms of memory and operations compared to other languages.

Now, if you are looking for a job that is related to C# Design Pattern then you need to prepare for the 2023 C# Design Pattern Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important C# Design Pattern Interview Questions and Answers which will help you get success in your interview.

In this 2023 C# Design Pattern Interview Questions article, we shall present 10 most important and frequently used C# Design Pattern interview questions. These questions are divided into two parts are as follows:

Part 1 – C# Design Pattern Interview Questions (Basic)

This first part covers the basic C# Design Pattern Interview Questions and Answers

Q1. What is Pattern Designs and explain its significance?

Answer:
Design Patterns are efficient solutions to the General Software Design problems. The common problems are resolved by applying these Design Patterns which are the best practices to obtain efficient solutions for the complex known and common problems in the design challenges of the software design and development processes. These design solutions for the common problems were obtained after performing several trial and error methods by many developers for a long time in many designs to obtain these effective solutions to the commonly known problems. There are different types of Design patterns. They are Behavioural Patterns, Creational Patterns, and Structural Patterns.

Q2. What are the different uses of Design Patterns?

Answer:
Below are the different uses of the Design Patterns –

1. Speeds up the development process
2. Ensures effective and efficient software designs
3. More reusability for the common problems across the design model
4. Enables code readability
5. Good documentation and easier to maintain for other developers
6. Robust applications can be developed
7. Ensures customer retention for delivering efficient and robust solutions

Q3. What are the different types of Design Patterns and explain?

Answer:
The different types of Design patterns are Behavioural Patterns, Creational Patterns, and Structural Patterns. They are explained as below.
Behavioural Pattern: The Behavioural Pattern is all about the communication between the several objects of the classes. It mainly concentrates on the communication and invocation between the objects.
Creational Pattern: The Creational Pattern is about the instantiation of the class and also further extends to the object creation. This category can be further divided into Class creational patterns and object creational patterns. The main theme used in this pattern is a delegation to get the work done. It mainly depends on the delegation model.
Structural Pattern: The Structural Pattern is about the composition of the classes and objects while interacting with several other classes. This ensures the application is more loosely coupled than getting complex.

Q4. What is Singleton Pattern and how can it be implemented in C#?

Answer:
This is the basic C# Design Pattern Interview Question asked in an interview. A Singleton Pattern is a design pattern that comes under the Creational design pattern which is used to instantiate only a single object from that class. Finally, that class will be confined only to a single object in its entire life cycle. The Singleton design pattern is very important in hiding the class instantiation functionality to be hidden from the other classes in order to maintain the object instantiation limitations for the purpose of application or design requirements to be fulfilled. Always only a single instance can be created from the Singleton Design pattern. In C# this can be implemented using the single constructor which is given with access keyword private and without any parameters i.e., default no-args constructor. This method does not provide any thread-safety. For any thread safety, pre-checks like null checks can be evaluated before proceeding with the next flow of execution in order to prevent the instantiation of other objects once a single object is created out of that class.

Q5. Which Design Pattern is used to implement any complex method or object?

Answer:
There are some cases where there will need to implement complex methods or objects such as where a method needs to be implemented with more than 6 or 7 arguments. In that case, the method is going to be complex and this results in poor quality of code. To avoid this problem, Builder Pattern can be used to implement an efficient way of handling and operating complex methods or objects. Builder Pattern will have a chain of methods and a build() method in order to be executed at the end of calling all the methods. This will construct a complex object easily by invoking in a chain method.

Part 2 – C# Design Pattern Interview Questions (Advanced)

Let us now have a look at the advanced Interview Questions.

Q6. What are the advantages of using Design Pattern with any Object Oriented Programming languages like C#?

Answer:
The advantages of using Design Patterns especially with Object-Oriented Programming Languages like C# or Java etc. are as below:

1. It gives a proven solution to a problem
2. Ensures loosely coupled application development
3. Enables instant high-level overview after l looking at the code immediately
4. Easier to understand
5. Easier to maintain and develop new features.

Q7. What is the prototype Design Pattern?

Answer:
The Prototype Design Pattern comes under the Creational Design Pattern which is used to clone the objects in the form of the prototypal instance. This can be implemented in C# programming language by declaring a base abstract class by using the clone() method.

Let us move to the next C# Design Pattern Interview Question.

Q8. What is the Factory Design Pattern?

Answer:
A factory Design Pattern is a Creational Design Pattern which is used to create instances of many derived classes. The name itself says that a Factory Design Pattern is used to instantiate many objects as required.

Q9. What is a Façade Design Pattern?

Answer:
This is the most asked C# Design Pattern Interview Questions in an interview. A Façade Design Pattern is a Structural Design Pattern which is implemented to represent a complete subsystem as a single class. This is efficient in case there is a huge number of classes in different areas.

Q10. What are the SOLID design principles?

Answer:
The SOLID Design Principles are the best-known principles in the area of Object-Oriented Software Design and Development. The five SOLID design principles are listed below:

1. Single Responsibility Principle (SRP)
2. Open/Closed Principle (OCP)
3. Liskov Substitution Principle (LSP)
4. Interface Segregation Principle (ISP)
5. Dependency Inversion Principle (DIP)

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