Importance of c# Interfaces

[Linoo]

Hello friends,
I am last year computer science student. I recently started learning c# language. In our last lecture we learn about c# Interfaces, but I didn't understand it clearly. Can anyone tell me Importance of c# Interfaces.
Thanks in advanced.

[Praetor]

I have written following program for you, in which I have use Interface. In following program I have defined the Itests.Class(Managers) as the one of the interface. I also create another class but I didn't declare it as interface. Just try to understand it.

public interface Itests
{
    void DoSomethings();
}

public class Managers:Itests
{
    public void DoSomething()
    {
        Console.WriteLine("test is started");
    }

}
class Employees
{
    public void DoSomethings()
    {
        Console.WriteLine("test is over ");
    }
}

class Programs
{
    static void Main(string[] args)
    {
        Manager ms = new Managers();
        ms.DoSomething();
        Employee es = new Employees();
        es.DoSomethings();
        Console.ReadLine();
    }
}

[Katty]

Using interface you can declare method in another interface without declaring new interface. But make sure that you have implement write interface otherwise it will give you error message. Using interface you can declare abstract methods in an abstract base class, because interface only gives description of method when you use this method in your program.

[kelfro]

Just try to understand following example. In this example I have use Interface. After learning following code you clearly understand concept of interface. To overcome multiple inheritance we use interface.

using System;

namespace ConsoleApplication1
{
   public class Mammals
   {
      protected string Characteristiss;
      public string characteristicss
      {
         get
         {
            return this.Characteristiss;
         }
         set
         {
            this.Characteristiss=value;
         }
      }
   }
   interface IIntelligences
   {

      bool intelligent_behavior();
   }

   class Humans: Mammals, IIntelligences
   {
      public Human()
      {
          characteristics = "Humans are mammalss";
      }


      public bool intelligent_behaviors()
      {
         Console.WriteLine("{0} and have intelligence",characteristics);
         return true
      }
   }
   class Whales: Mammals
   {
      public Whale()
      {
         characteristicss = "Whale are mammalss";
         Console.WriteLine("{0}",characteristics);
      }
   }
   class InterfaceApp
   {
      public static void Main(string[] args)
      {
         Whale whales = new Whale();
         Human humans = new Human();
      
         IIntelligence humanIQs = (IIntelligences)humans;
         humanIQs.intelligent_behaviors();

         Console.Reads();
      }
   }
}

[Zecho]

To use multiple class in one program we use interface. First you have to declare one interface in each class. After that invoke each interface from each class, but make sure that they must have at least one method. For eg.

       public Interface Animals
            {
                public void Talks();
                public void Eats();
            }

now add another method.

 public Interface Animals
            {
                public void Talks();
                public void Sleeps();
                public void Eats();
            }