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Top 14 C# Design Patterns Interview Questions and Answers

07/Sep/2021 | 10 minutes to read


Here is a List of essential C# Design Patterns Interview Questions and Answers for Freshers and mid level of Experienced Professionals. All answers for these C# Design Patterns questions are explained in a simple and easiest way. These basic, advanced and latest C# Design Patterns questions will help you to clear your next Job interview.

C# Design Patterns Interview Questions

C# Design Patterns Interview Questions and Answers

These interview questions are targeted for Design Patterns. You must know the answers of these frequently asked Design Patterns interview questions to clear the interview. C# Programming language is used to show the Design Patterns examples. Design Patterns are technology agnostic means - These are required for all developers like Java Developer, .Net Developer, JavaScript, iOS, C++ etc.

1. What is a design pattern?

Design Pattern can be defined as

  • A solution to a problem which occurs very commonly in software design.
  • A solution used by programmers to solve common problems in different situations.
  • Not tied to specific problems, Provides general solutions.
  • Not a ready to use design that can be directly fit into source code.
  • A solution that can be customized to solve a particular problem.

2. Explain the different categories of Design Patterns?

Design Patterns have been categorized into three types based on the problem they solve.

  • Creation Design Patterns
  • Structural Design Patterns
  • Behavioural Design Patterns

3. What problem design patterns solve?

Design Patterns are the solutions to common occurring general problems. They are not the exact solution of any problem, rather you need to customize them. For example, When you want a single instance of any class then you implement a singleton design pattern that you can customize as per your need like thread safe implementation.

4. What is the Bounded Context design pattern?

Bounded Context design pattern is a concept of DDD - Domain-Driven design. Domain-Driven design deals with large domain models by dividing them into bounded contexts. A domain model incorporates both data and behavior for a domain.
In other words, the Bounded context design pattern is used to deal with large domain models in DDD. MicroServices mainly use this design pattern as they are technology agnostic and domain specific.

5. Explain Singleton Design Pattern.

Singleton Design Pattern is a software pattern that prevents the creation of more than one instance of a class. This pattern is useful when only one instance is required across the system to coordinate with actions. In simple words, You will be able to create only a single instance of a class with Singleton Design Pattern. This Pattern is one of the twenty three Gang of Four - design patterns.

6. Explain How will you implement thread safe singleton design pattern in C#?

You can implement thread safe singleton design pattern using the concept of lock in C# as below.

    public class Singleton
        private static object _myLock = new object();
        private static Singleton _singleton = null;

        private Singleton() { }

        public static Singleton Instance()
            if (_singleton is null) // The first check
                lock (_myLock)
                    if (_singleton is null) // The second (double) check
                        _singleton = new Singleton();

            return _singleton;
You can also use Lazy class to create a singleton design pattern in C# 4.0 or later, internally it uses double-checked locking by default.

    public class Singleton
        private static readonly Lazy _singleton = new Lazy(() => new Singleton());
        private Singleton() { }
        public static Singleton Instance => _singleton.Value;

7. Explain Factory Pattern.

8. Describe Repository Design Pattern. Have you implemented a repository design pattern in C#?

9. What is the difference between Singleton design pattern and Static class in C#?

10. Describe the Dependency Injection (DI) design pattern?

Dependency Injection design pattern is a technique to achieve the Inversion of Control (IoC - inverting the typical compile-time dependency) between classes and their dependencies. Dependency Injection design pattern comes along with other patterns such as logging, options and configuration in .NET. For more visit Dependency Injection C# and IoC.

11. What is the component-service design pattern?

12. What is the dispose design pattern in C#?

Some General Interview Questions for C# Design Patterns

1. How much will you rate yourself in C# Design Patterns?

When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like C# Design Patterns, So It's depend on your knowledge and work experience in C# Design Patterns.

2. What challenges did you face while working on C# Design Patterns?

This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related to C# Design Patterns in your Project.

3. What was your role in the last Project related to C# Design Patterns?

It's based on your role and responsibilities assigned to you and what functionality you implemented using C# Design Patterns in your project. This question is generally asked in every interview.

4. How much experience do you have in C# Design Patterns?

Here you can tell about your overall work experience on C# Design Patterns.

5. Have you done any C# Design Patterns Certification or Training?

It depends on the candidate whether you have done any C# Design Patterns training or certification. Certifications or training are not essential but good to have.


We have covered some frequently asked C# Design Patterns Interview Questions and Answers to help you for your Interview. All these Essential C# Design Patterns Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any C# Design Patterns Interview if you face any difficulty to answer any question please write to us at Our IT Expert team will find the best answer and will update on the portal. In case we find any new C# Design Patterns questions, we will update the same here.