What is difference between delegate and interface

Question

i know delegate is function pointer and interface and abstract is part of OOPS for implementing polymorphism.

so why people ask often in interview what is difference between delegate and interface ?

delegate and interface use for same purpose?

anyone can explain what is difference between delegate and interface with sample code and example ?

thanks

Answer 1

You will get better understanding here

http://www.dotnetfunda.com/articles/show/3015/differences-between-delegates-and-interfaces-in-csharp

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MD. ROKON-UZ-ZAMAN

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Answer 2

why people ask often in interview what is difference between delegate and interface ?  That's a good interview question too!

delegate and interface use for same purpose?  No.

anyone can explain what is difference between delegate and interface with sample code and example ?

A delegate is a type that represents references to methods with a particular parameter list and return type.

An interface contains definitions for a group of related functionalities that a class or a struct can implement.

Compare Delegates vs. Interfaces

delegate int BinaryOperator( int lhs, int rhs );

interface IBinaryOperator
{
    int Perform( int lhs, int rhs );
}

class Add : IBinaryOperator
{
    public int Perform( int lhs, int rhs )
    {
        return lhs + rhs;
    }
}

class Program
{
    static void Main( string[] args )
    {
        IBinaryOperator obj = new Add();
        BinaryOperator op = obj.Perform;

        int lhs = 3;
        int rhs = 5;
        int answer_1 = obj.Perform( lhs, rhs );
        int answer_2 = op( 3, 5 );
    }
}

Answer 3

Sorry......from the above code it is not clear the difference between delegate and interface

Answer 4

They are totally different.

An Interface is a way to define classes, in order to force the person who creates a class to have certain things in it.

A Delegate is a way to call a function as a variable.

 

Noam B.

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Answer 5

Sorry......from the above code it is not clear the difference between delegate and interface

For those who enjoy learning from failure, here are a few negative result experiments for you to attempt.

• Try to derive a class from a delegate.
• Try to declare a variable of some interface type and assigning a delegate to it.
• Try to declare an event of type interface.
• Try to declare a delegate that implements multiple methods.
• Try to combine interfaces using the + operator to create a multicast interface (as you would with a multicast delegate)

(Pro tip:  None of these experiments will succeed, because delegates and interfaces are totally different things.)

(Pro tip #2:  Replace the words "Try to" in the above list with "You can't", if you prefer to read a list of facts.)

Answer 6

Hi Mou_inn,

Thank you for posting here.

For your question, I provided two examples for reference.

Interface is used to defined the same behavior and abilities for some classes(like defined what it is) generally.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace @interface
{
    class Program
    {
        static void Main(string[] args)
        {
            Transaction t1 = new Transaction("001", "8/10/2016", 78900.00);
            Transaction t2 = new Transaction("002", "9/10/2016", 451900.00);
            t1.showTransaction();
            t2.showTransaction();
            Console.ReadKey();
        }
    }
    public interface ITransactions
    {
        // interface members
        void showTransaction();
        double getAmount();
    }

    public class Transaction : ITransactions
    {
        private string tCode;
        private string date;
        private double amount;
        public Transaction()
        {
            tCode = " ";
            date = " ";
            amount = 0.0;
        }

        public Transaction(string c, string d, double a)
        {
            tCode = c;
            date = d;
            amount = a;
        }

        public double getAmount()
        {
            return amount;
        }

        public void showTransaction()
        {
            Console.WriteLine("Transaction: {0}", tCode);
            Console.WriteLine("Date: {0}", date);
            Console.WriteLine("Amount: {0}", getAmount());
        }
    }
}

Delegate is used to achieve events and callback methods generally. 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace @delegate
{
    delegate int NumberChanger(int n);
    class Program
    {
        static void Main(string[] args)
        {
      
            NumberChanger nc1 = new NumberChanger(AddNum);
            NumberChanger nc2 = new NumberChanger(MultNum);
  
            nc1(25);
            Console.WriteLine("Value of Num: {0}", getNum());
            nc2(5);
            Console.WriteLine("Value of Num: {0}", getNum());
            Console.ReadKey();
        }
        static int num = 10;
        public static int AddNum(int p)
        {
            num += p;
            return num;
        }

        public static int MultNum(int q)
        {
            num *= q;
            return num;
        }
        public static int getNum()
        {
            return num;
        }
    }
}

I hope this would be helpful to you.

Best Regards,

Wendy

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