IList<string> stringList = new List<string>()

You really need to learn the basics of c# and OOPs concepts.

Interface means a Menu card that can have multiple implementations any class that inherit from the interface are bound to implement the properties and method of that interface.

Being a parent an Interface can be pointed to any of its child and this is largest benifit of any OOPs language i think.

I can't consider a language without interface, because i really can't see a programing world without polymorphism and interface are the main source to achieve polymorphism means changing the behaviour at run time.

This is the reason Dependency injections revolves around Interfaces to achieve loose coupling and independent architectural designs.

public interface IEmployeeBL
{
IEnumerable GetAll();
}
//First omplementation
public Class EmployeeBL1 :IEmployeeBL
{
IEnumerable GetAll()
{
var emps= new List()
{
new Employee(){Name="Sachin", Salary="1200000"},
new Employee(){Name="Anupam", Salary="67000"},
};
return emps;
}
}
// 2nd implementation
public Class EmployeeBL1 :IEmployeeBL
{
IEnumerable GetAll()
{
return EmployeeDal().GetAll(); // fetching from some DB
}

Now UI layer we can oint to any implementation at run time

public class HomeController:Controller
{
private IEmployeeBL _empBL;
public HomeController(IEmployeeBL empBL) // DI
{
_empBL=empBL;
}
public IEnumerable GetEmployees()
{
return _empBL.GetAll(); // will be resolved at run time
}
}

In short

public class List:IList
{
// some methods of List
Find(Func<>);
Where(Func<>);
etc etc
}

so it can point to any list

IList strings= new List();
IList emps=new List();

1 Reply

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Sachin Singh4y ago
You really need to learn the basics of c# and OOPs concepts.
Interface means a Menu card that can have multiple implementations any class that inherit from the interface are bound to implement the properties and method of that interface.
Being a parent an Interface can be pointed to any of its child and this is largest benifit of any OOPs language i think.
I can't consider a language without interface, because i really can't see a programing world without polymorphism and interface are the main source to achieve polymorphism means changing the behaviour at run time.

This is the reason Dependency injections revolves around Interfaces to achieve loose coupling and independent architectural designs.
public interface IEmployeeBL
{
IEnumerable GetAll();
}

//First omplementation
public Class EmployeeBL1 :IEmployeeBL
{
IEnumerable GetAll()
{
var emps= new List()
{
new Employee(){Name="Sachin", Salary="1200000"},
new Employee(){Name="Anupam", Salary="67000"},
};
return emps;
}
}
// 2nd implementation
public Class EmployeeBL1 :IEmployeeBL
{
IEnumerable GetAll()
{
return EmployeeDal().GetAll(); // fetching from some DB
}
Now UI layer we can oint to any implementation at run time
public class HomeController:Controller
{
private IEmployeeBL _empBL;
public HomeController(IEmployeeBL empBL)  // DI
{
_empBL=empBL;
}
public IEnumerable GetEmployees()
{
return _empBL.GetAll(); // will be resolved at run time
}
}
In short
public class List:IList
{
// some methods of List
Find(Func<>);
Where(Func<>);
etc etc
}
so it can point to any list
IList strings= new List();
IList emps=new List();