Difference Between Abstract Class and Interface in C#

What is an Abstract Class?

An abstract class is a common feature of object-oriented programming languages. In simple words, an abstract class is the definition of a category of objects containing a single or multiple abstract methods. In C#, objects or classes are translatable into specific characteristics that are important to a program’s operation. When a class is defined as abstract, no object can be created from it. In terms of utility, this prevents the code from being used inappropriately.

Abstract classes are often thought of in comparison with concrete classes. This type of class is devoid of any abstraction and allows for possible use in code. Unlike an abstract class, a concrete class occurs by default. Abstract classes in programming are used chiefly for pragmatic purposes, e.g., keeping the code clean and creating the environment for efficient coding. To access an abstract class, it is necessary that it be inherited from another class.

Abstraction is advantageous because it hides details and displays only functionality. A class or method can be made abstract by using the word “abstract” prior to it. The same keyword can be applied to events and properties in the language. As a matter of fact, abstract classes are relatively faster in their functionality and make defining fields and constants equally possible.

What is Interface in C#?

Interface in C# is a crucial component that includes the declarations of correlating functionalities. The same interface tries to achieve regulation between related functionalities. Interface in C# hinges on the declaration of events, indexers, events, and methods in the language. The interface lacks instance fields and does not entail fields and constructors. The defining keyword for it is “interface” – to be used.

A colon “:” can be used to implement an interface or more. There is another way to implement an interface: explicit implementation. The aforesaid strategy is considered ideal when implementing multiple interfaces in C# is needed. In terms of speed, interfaces are observed to be slow. Moreover, it is impossible to find fields while using the interface. Still, you can use a single interface to extend multiple interfaces while programming. By default, the interface in C# lacks access modifiers and does not allow a static member.

Many amateur programmers do not know that an interface does not have constructors. Without knowing this, they make a grave mistake if they venture to create a program of a specific kind. The interface is also confined to containing a mere incomplete member. Unlike abstract class, it supports multiple inheritances. Its properties can be used in any Java environment – making it more flexible for later usage.

Difference Between Abstract Class and Interface in C#

  1. An abstract class does not allow multiple inheritances, whereas Interface in C# supports multiple inheritances.
  2. An abstract class does contain the data member, whereas Interface in C# lacks the data member.
  3. An abstract class can have access modifiers, whereas Interface in C# does not contain access modifiers by default
  4. An abstract class has a static member if it is static, whereas Interface in C# does not have a static member.
  5. An abstract class works relatively faster, whereas Interface in C# is recorded to be somewhat slower.

Comparison Between Abstract Class and Interface in C#

Parameters of ComparisonAbstract ClassInterface in C#
Multiple InheritanceNot AllowedSupported
Data MemberPresentNot Present
Access ModifiersAvailableNot Available
MemberStatic if CompleteNot Static
SpeedRelatively FasterRelatively Slower


  1. https://link.springer.com/chapter/10.1007/978-1-4842-7322-7_2
  2. https://link.springer.com/chapter/10.1007/978-1-4471-0193-2_9