what is interface ? and what should it contains?

Question

Hi, interface contain only declaration no definition?

Francis · Answer

public interface Myinterface { TKey Id { get; } string UserName { get; set; } } but i am not getting what is purpose of writing like above OK. As per the code, you are trying to create "Generic Interface". For generic type parameters, the out keyword specifies that the type parameter is covariant. You can use the out keyword in generic interfaces and delegates. Below urls are give a detailed lookup int these topics: Generic Interface: http://www.functionx.com/csharp/interfaces/cugi.htm Covariant interface: https://msdn.microsoft.com/en-us/library/dd469487.aspx Contravarient interface: https://msdn.microsoft.com/en-us/library/dd469484.aspx Hope this helps!

Rajeesh Menoth · Answer

Hi, Interface is mainly used for declaration purpose.Abstract is mainly used for modification.Abstract is faster than Interface but Multiple Inheritence we need Interface. Reference : http://www.c-sharpcorner.com/UploadFile/sekarbalag/interface-best-example-in-csharp/ http://www.codeguru.com/csharp/csharp/cs_syntax/interfaces/article.php/c7563/Interfaces-in-C.htm

Ravi Patel · Answer

Sir we can write like bellow public interface Myinterface { TKey Id { get; } string UserName { get; set; } } } but i am not getting what is purpose of writing like above

Raja T · Answer

Hello Ravi, No, The type is used only as a return type of interface methods and not used as a type of method arguments. More details check out below links https://msdn.microsoft.com/en-us/library/dd997386.aspx https://msdn.microsoft.com/en-us/library/512aeb7t.aspx http://www.functionx.com/csharp/interfaces/cugi.htm

Ravi Patel · Answer

can we write like this public interface Myinterface { TKey Id { get; } string UserName { get; set; } } }

Raja T · Answer

Hello Ravi, An interface looks like a class, but has no implementation. The only thing it contains are declarations of events , indexers , methods and/or properties . The reason interfaces only provide declarations is because they are inherited by classes and structs , which must provide an implementation for each interface member declared. more details check out below links http://www.c-sharpcorner.com/UploadFile/sekarbalag/interface-best-example-in-csharp/ http://www.codeproject.com/Articles/18743/Interfaces-in-C-For-Beginners http://www.csharp-station.com/Tutorial/CSharp/Lesson13