Interface in .Net

Question

Team As I know that we can't create instance for Interface in .Net But I m bit confuse with some scenario's like Interface IA { add(); } Class A : IA { add() { } } NowI can use IA obj = new A() Can you please explain briefly & give some reference links to understand with core. Thanks

SIVA · Answer

Ranjit Same question is not answer for that. Please understand the question properly and answer. Thanks

SIVA · Answer

Thanks Vulpes

Vulpes · Answer

Although you can't create instances of an interface you can declare variables and parameters of the interface type. You can assign to such variables or parameters instances of classes or structs which implement the interface. So in your example code you have this line: IA obj = new A(); which declares a variable obj of the interface type IA and then assigns to it an instance of the class A which implements IA. Because we know that any class (or struct) which implements IA must have a public add method we also know that we can do this: obj.add(); In general you can only call those methods of A which implement the IA interface through the variable obj. The variable doesn't know anything about other methods or properties which A may contain. The purpose of allowing variables and parameters of interface types is to allow you to write generic code in relation to any class or struct which implements the interface even those those types may otherwise have no relation to each other. For more on interfaces check out this link: http://msdn.microsoft.com/en-us/library/ms173156.aspx

Ranjit Powar · Answer

Try this interface I1 { void add(); } class Program:I1 { public void add() { Console.Write(Hi); } static void Main(string[] args) { I1 i = new Program(); i.add(); } }