How to Pick Abstract Class Or Interface in C#

R M Shahidul Islam Shahed
3 min readNov 28, 2023

In the intricate realm of C# programming, the decision to choose between an abstract class and an interface is a nuanced process that shapes the structure and behavior of software. As developers grapple with the task of designing robust and maintainable systems, the question arises: How to Pick Abstract Class or Interface in C#? This pivotal decision-making process involves a thoughtful evaluation of design goals, coding patterns, and the specific needs of the application at hand. Each choice, whether it be an abstract class or an interface, brings unique advantages and considerations to the table.

When to Use an Abstract Class and When to Use an Interface in C#

In C#, both abstract classes and interfaces provide mechanisms for defining contracts that classes must adhere to. However, there are key differences between the two, and the choice between using an abstract class or an interface depends on the design goals and requirements of your application.

Here are some guidelines to help you decide when to use an abstract class and when to use an interface:

Use an Abstract Class when?

  1. Common Implementation: If you have a base class that contains common functionality shared among derived classes, an abstract class is a suitable choice. Abstract classes can provide a partial implementation of methods along with abstract members that must be implemented by derived classes.
  2. Access Modifiers: Abstract classes allow you to specify access modifiers on methods, fields, and properties. This enables you to control the visibility of members in a more fine-grained manner.
  3. Constructor Support: Abstract classes can have constructors, which is beneficial if you need to enforce certain initialization steps in derived classes.
  4. Versioning: If you anticipate adding new methods or properties in the future and want to provide default implementations for existing derived classes without breaking their functionality, abstract classes are more flexible in this regard.
public abstract class MyBaseClass
public void CommonMethod()
// Common implementation

public abstract void AbstractMethod();

Use an Interface when?

  1. Multiple Inheritance: C#…