What is Interface?
An interface is collection of methods, properties, indexers
and events with only signatures. Means In interface Methods, properties,
indexers and events do not have their definition. So an Interface allows you to
define behavioral characteristics and apply those behaviours to Class that
implements this Interface. Example
public interface IHoliDay
{
List<DateTime>
GetListOfHoliday();
}
Or
interface IHoliDay
{
List<DateTime> GetListOfHoliday();
}
If you use public List<DateTime>
GetListOfHoliday() an error occurred.
Error 1 The modifier 'public' is not valid for
this item .
So there is no need of
modifiers for Interface members. Interface members are automatically public and
cannot be static.
Why Interface is came in existence?
Interface is mainly used for two reasons
·
C# does not support multiple inheritances, so by
using Interface, A class can implement multiple interfaces to achieve multiple inheritances.
public class HoliDay : Class1, Interface1,Interface2,Interface3
{
}
·
Data Hiding
You can call class members using
Interface.
class Program
{
static void Main(string[]
args)
{
//Hiding
the Holiday class object
IHoliday
ii = new Holiday();
ii.GetHoliDayList();
Console.WriteLine(ii.val);
}
}
public interface IHoliday
{
string
val{get; set;}
List<DateTime> GetHoliDayList();
}
public class Holiday : IHoliday
{
public String val{ get; set;}
List<DateTime> hlist = new
List<DateTime>();
public List<DateTime> GetHoliDayList()
{
//code
val = "Class
Members";
Console.WriteLine("Calling by interface");
return
hlist;
}
}
Interface also used to make your code more reusable, maintainable,
and scalable and provides the concept of component based programming.
Suppose you have two interfaces with method with same name. How to
implement both in same class?
User Intafacename.MethodName()
{
}
Example:
class Program
{
static void Main(string[] args)
{
//Hiding the Holiday class object
IOfficeHoliday iioffice = new
Holiday();
iioffice.GetHoliDayList();
IGuzzatedHoliday iiGuzzated = new Holiday();
iiGuzzated.GetHoliDayList();
//Console.WriteLine(ii.val);
}
}
//first interface
public interface IOfficeHoliday
{
List<DateTime>
GetHoliDayList();
}
//second interface
public interface IGuzzatedHoliday
{
List<DateTime>
GetHoliDayList();
}
public class Holiday : IOfficeHoliday,
IGuzzatedHoliday
{
List<DateTime>
hlist = new List<DateTime>();
//Method definintion for first interface
List<DateTime>
IGuzzatedHoliday.GetHoliDayList()
{
//code
Console.WriteLine("IGuzzatedHoliday
Method");
return hlist;
}
//Method definintion for second interface
List<DateTime>
IOfficeHoliday.GetHoliDayList()
{
//code
Console.WriteLine("IOfficeHoliday
Method");
return hlist;
}
}
//here if you use public
with method definition in class that implements both of interfaces, an error occurred.
What is the use of is and as operator with respect to Interface concept?
The is and as operators can be used to determine whether an
interface is implemented by an object.
Holiday hh = new Holiday();
IHoliday iholiday = hh as
IHoliday;
if (hh is IHoliday)
{
Console.WriteLine("Holiday class implemented IHoilday");
}
Comments if you have
other possible interview FAQ for Interface in C#.
