As the answer posted by Mr.Raj Kumar, This answer is absolutely wrong. The difference between Abstract class and Interface is, if you implement abstract class then it is not mandatory to implement all the defined methods and properties in the derived class but in case of interface implementation it is must to implement each and every methods and properties defined in the interface class otherwise the application will not compile. Birendra Kumar Singh

Read my trilogy articles about this issues Here is the link of the first one: http://www.c-sharpcorner.com/UploadFile/yougerthen/104232008193919PM/1.aspx?ArticleID=0ba5516c-764e-443e-80ef-a7fc2862d6ab

An abstract class and Interface both have method only but not have body of method.The difference between Abstract class and An Interface is that if u call Ablstract class then u have to call all method of that particular Abstract class but if u call an Interface then it is not necessary that u call all method of that particular interface.Method OverLoading:-Return type, Parameter type, parameter and body of method number may be different.Method Overriding:- Return type, Parameter type, Parameter Number all must be same . Only body of method can change