What is Interface in C#? | Definition, Components, Pros and Cons

The purpose of an interface is to demarcate what it is that any given class does. The role of an interface is the definition of its members. The interface cannot implement the members itself; it is entirely dependent upon the class which inherits and implements.

Any interface can comprise methods, events, properties, and indexers, but the interface can have only the bare signatures of it. The declaration function is the primary task of an interface – it lacks implementation and functionality. Thus, it only provides an outline of the functions of a class that inherits and implements its properties.

Different components of an Interface in C#

A good way to understand the concept of an interface is to imagine it as an abstract class devoid of the capacity for implementation. The following points further shed light on other aspects and features of the interface in C#.

  1. Since implementation has no role to play in interface, it has the ability to be reused multiple times. Since it is the primary structure or blueprint on which a class is based, it can be used to create codes of different kinds but with a degree of commonality.
  2. By implementing several interfaces, one can effectively bypass the issue of C# not supporting inheritance from numerous classes at once.
  3. An interface is generally always fully implemented because it dictates what a class can do. It is also a great way to group together classes which inherit from the same interface. The interface is also effective in enabling communication between objects and methods of different classes.
  4. Modifications in behaviour of classes or their definition and functionality become simpler and easier because of the interface.
  5. An interface necessarily contains only methods. It is always defined by the modifier for public access.

Advantages of Interface in C#

  1. Interface makes the grouping and sorting of codes an easier task because of its reusability and its definition of the separate components of any class. It is also flexible enough to accommodate changes in future class definitions.
  2. It can thus also be used to unravel and study the relationships between dependent class objects. At the same time it reduces the dependency of one class on another.
  3. Implementation of multiple inheritances and the loose coupling of applications is possible because of the basic characteristics of interface in C#.
  4. It is often preferable to abstract class by programmers due to this one significant advantage – while a class cannot inherit more than a single abstract class, it can do so in case of interface.
Difference Between C++ and Java (With Table)

Disadvantages of Interface in C#

  1. Implementation of multiple interfaces at once can create errors such as conflicting members. A programmer also has to bear in mind that an interface does not have too many methods, because this makes implementation of all the methods by a class complicated.
  2. An interface can only be used to define the common elements of a set of classes, it cannot be modified to include details specific to a few. The details would then be implemented by all classes in question.


  1. https://www.scientific.net/AMR.622-623.1929
  2. https://dl.acm.org/doi/book/10.5555/1162257