This article explains interface in C#.
An Interface is a contract that is implemented. It has just the method definition inside. Implementation of these methods is done by the class implementing the interface. We can use properties, indexers in the inteface too, but we can just define them. Implementation will be done by the implementing class of the interface.Interface is by default public in nature. The class inheriting the interface has to compulsorily implement all the interface methods. Let us check out the syntax for interface.Syntax
Programming Strings using C#