Difference Between Abstract Class and Interface In C# (With Table)

As all of us recognize, Abstract class and Interface in C# are each programming-orientated and assist in subjects that can be object-oriented like encapsulation, abstraction, inheritance, and polymorphism. But, there are a lot of differences between them. They both differ from each other in terms of functionality. In the former, we can create and implement functionality: in the latter, we can only define functionality.

Abstract Class vs Interface In C#

The main difference is that Abstract Class creates a way to execute the abstraction in C#. On the other hand, Interface can only declare methods, properties, or events but not execute them. Moreover, we also know that the Abstract class runs faster than the Interface in C#. Also, the former includes static members, while the latter does not.

In general, abstract classes provide functionality that derived classes must implement. It gives us a way to attain abstraction C#. We cannot initiate abstract classes directly. It is compulsory to have at least one abstract mechanism marked “abstract” by the keyword or modifier. In simpler words, a base class from the class hierarchy is defined by the abstract class.

On the other hand, an interface is a class that can create mechanisms, events, or properties but cannot implement them. We can implement them only when an interface class that applies interface simplicity or explicitly allows implementation for them. Moreover, the interface in C# is a slow process.

Comparison Table Between Abstract Class and Interface In C#

Parameters of comparisonAbstract ClassInterface
DefinitionAn Abstract class is a class that cannot be instantiated and is typically implemented as a class with one or more pure abstract functions, according to the standard definition.On the contrary, an interface is a definition of which member functions a class that inherits this interface must implement. In other words, an interface explains the class’s functionality.
ImplementationIn C#, abstract classes, like many other regular class concepts, have their implementation, in addition, to their declaration.On the contrary, an interface cannot provide the implementation. Hence, only the class implements it can provide the implementation.
ConstructorAbstract class, the same as other C# classes, has a function Object that creates an instance of the abstract class so that non-static functionalities can be used.We cannot completely instantiate an interface because it lacks constructors, but we can access its techniques by making an instance of a class that implements it.
InheritanceA class can only extend one other class according to the C # configuration. As a result, an abstract class cannot support multiple inheritances.A class can implement numerous interfaces in the case of an interface, letting the interface have multiple inheritances.
ModifiersEven though abstract classes are similar to other conventional classes in C#, they can have various access modifiers such as public, private, and protected.Interfaces must design for other classes to implement their methods; hence they can only have public access modifiers.

What is an Abstract Class in C#?

An abstract class is a non instantiated imperfect or unique class. The goal of an abstract class is to offer a model for derived classes and; to provide some rules that the classes must follow when inheriting an abstract class.

 We can use an overriding keyword to execute an abstract method in all non-abstract classes. The abstract technique is now in the non-abstract class after being overridden. This class can derive from yet another class, that can then override the same abstract method.

An abstract class can add modifiers for method, attributes, and other properties. Constants and fields are both possible in it. It can also execute a property. Moreover, it has constructors and destructors. 

But, an abstract class is devoid of supporting numerous inheritances. Also, structures cannot inherit from an abstract class.

What is an Interface in C#?

An interface is a class that is devoid of performing the implementation. The only thing it includes are expressions of events, indexers, methods, and properties. It can only incorporate declarations because it is inherited by struts and classes, which must supply an implementation for each interface member stated.

There are some satisfactory features of the interface rather than declaration of events. They are ideal for creating architectures that are plug-and-play in nature, with components that can exchange out at will. Because all interchangeable elements use the same interface, they can be used together instead of additional programming. Each element is compelled by the interface to disclose particular public members that will use in a specific way. 

Moreover, we shall also use an interface as they make it possible to create classes that inherit from other classes and include some of their parent’s members as well as your own.

Main Differences between Abstract Class and Interface In C#

  1. An abstract class can provide both a declaration and a definition, but cannot provide a complete abstraction. On the other hand, the interface can supply in-depth abstraction, but cannot bring forth a declaration.
  2. Achieving multiple inheritances is not desirable in the case of abstract class in C#. However, an interface in C# can deliver multiple inheritances. 
  3. An abstract class has access to numerous modifiers, namely, private, public, internal, and protected. Whereas the interface only has access to public modifiers because, by default, the settings are always public.
  4. We can reveal a member field in the abstract class, but the interface is bereft of any declaration. 
  5. We can interpret abstract class applying the keywords static, virtual, abstract, or sealed. On the other hand, this is not within reach of the interface in C#.


Therefore, abstract class and interface in C# are much different from each other. An abstract class is faster than the interface is C#. The former can implement a functionality whereas, the latter cannot. Furthermore, only the interface in C# can attain multiple inheritances, not an abstract class. Also, it is necessary to add that the abstract class includes constructor but not static members whereas, the interface in C# does not include constructor but static members. Lastly, the abstract class has numerous modifiers but interface only one.


  1. https://link.springer.com/chapter/10.1007/978-1-4842-7322-7_2
  2. https://www.scientific.net/AMR.622-623.1929