what is interface ? and what should it contains?

Ravi Patel

10y735.NET

Hi,

interface contain only declaration no definition?

6 Replies

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Francis Susaimichael10y ago
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 Menoth10y ago
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 Patel10y ago
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 T10y ago
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 Patel10y ago
can we write like this

public interface Myinterface
{

TKey Id { get; }

string UserName { get; set; }
}
}
Raja T10y ago
Hello Ravi,
An interface looks like a class, but has no implementation. The only thing it contains are declarations of events, indexers, methodsand/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