Delegates in C#- 2

1.

 namespace DelegateEx

{

  public delegate int myDelegate(int x, int y);

  public delegate string mydelString(string fname, string lname);

    class Program

    {

       public static void Main(string[] args)

        {

            myDelegate del = new myDelegate(Math.Add);

            del += Math.Subtract;

            int result =  del(10,6);

            del += Math.Multiply;

            int r = del(3, 4);

            //myDelegate m = Math.Add;

            //int res = m.Invoke(2, 3);

           // int res = del.Invoke(6, 7);

            Console.WriteLine(result);

            Console.WriteLine(r);

            mydelString d1 = null;

            d1 += Math.GetFullName;// static methods can only be accessed from other static methods, and here Main and GetFullName are both static.

      string res = d1("test", "name"); // d1.Invoke("test", "name");

            Console.WriteLine(res);

            Console.ReadLine();

        }

      

    }

    public class Math {

        public static int Add(int a, int b)

        {

            return a + b;

        }

        public static int Multiply(int a, int b)

        {

            return a*b;

        }

        public static int Subtract(int a, int b)

        {

            return a - b;

        }

     public static string GetFullName(string fname, string lname)

        {

            return "The fullName is " + fname + " " + lname;

        }

    }

}

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2.

public partial class multicast : System.Web.UI.Page

{

    public delegate void ProgressReporter(int percentComplete);

    protected void Page_Load(object sender, EventArgs e)

    {

    }

    // create a delegate, assign methods to it, then invoke it.

    // This is time consuming method...so we need to know its progress.

    // so we give a delegate parameter and ask it to fire it.. to let the subscribers know about progress.

    public void HardWork(ProgressReporter pr) 

    {

        for (int i = 0; i < 10; i++)

        {

            pr(i * 10); // invoking the delegate

            System.Threading.Thread.Sleep(100);

        }

    

    }

    public void WriteProgressToConsole(int percent)

    {

        Response.Write("WriteProgressToConsole value: " + percent);

    }

    public void WriteProgressToFile(int percent)

    {

        Response.Write("WriteProgressToFile value: " + percent);

      

    }

    protected void Button1_Click(object sender, EventArgs e)

    {

        ProgressReporter p = WriteProgressToConsole; // assigning methods to delegate

        p += WriteProgressToFile;

        HardWork(p);

     

    }

     

}

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 3.

public partial class delegate1 : System.Web.UI.Page

{

    public delegate int Transform(int x);

    public delegate int TransformArray(int x);

    public delegate bool delIsEven(int x);

    protected void Page_Load(object sender, EventArgs e)

    {

    }

   

    //public int Square(int a)

    //{

    //    return a * a;

    //}

    // or the above method can also be declared like this below.

    int Square(int a) => a * a;

    int SquareArrayElement(int a) => a * a;

    bool MethodIsEven(int a) => (a % 2 == 0) ? true : false;

    protected void Button1_Click(object sender, EventArgs e)

    {

        //Transform t = new Transform(Square); // or like below

        Transform t = Square;

        //int result= t(6); 

        // or like this below

        int result = t.Invoke(6);

        Response.Write("The delegate return value is: " + result + "</br>");

       

        TransformArray delarray = SquareArrayElement; // assigning methods to Delegate.

        delIsEven dIsEven = MethodIsEven;

        int[] myArray = { 2, 3, 4, 5, 6, 7, 8 };

        int[] finalArray = MethodToSquareArrayElement(myArray, delarray); // passing delegate as parameter

        for (int i = 0; i < finalArray.Length; i++)

        {

            string flag = "";

            if (dIsEven(finalArray[i]))

            {

                flag = "It is Even";

            }

            else

            {

                flag = "It is Odd";

            }

            Response.Write(finalArray[i] + " " + flag + "</br>");

        }

        //for (int i = 0; i < myArray.Length; i++)

        //{

        //    // int result1 = SquareArrayElement(myArray[i]);

        //    int result1 = delarray.Invoke(myArray[i]);

        //    Response.Write(result1 + "</br>");

        //}

    }

    public int[] MethodToSquareArrayElement(int[] arr, TransformArray del) // passing delegate as parameter.

    {

        for (int i = 0; i < arr.Length; i++)

        {

            arr[i] = del(arr[i]); //

            // above line we can also write as i.e we can also directly pass the method name, but we preferred to pass delegate ref. above.

            //  arr[i] = SquareArrayElement(arr[i]);

            // ie. A Delegate variable can be assigned to a method at run time. This is useful for writing plugin methods.

        }

        return arr;

    }

}

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