Concepts of Anonymous Method,Lambda Expression,func, actions,Predicates and Expression Trees

Anonymous  methods in C#.net  :

Anonymous methods is a new language feature in C# 2.0, Anonymous methods allow us to define a code block where a delegate object is acceptable. This facility saves us an extra step of creating a delegate for small code blocks that we want to pass to a delegate. It also removes the cluttering of small methods in the class code. Let us say, for instance, that we have a string collection class named MyCollection. This class has a method that retrieves all the items in the collection that satisfies a user supplied criteria, i.e., the caller decides whether a particular item in the collection qualifies for being retrieved as part of the return array from this method.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Diagnostics;

namespace AnonymousMethodsandDelegates

{

    class Program

    {

        delegate int PointToAddFunction(int num1, int num2);

        static void Main(string[] args)

        {

            Stopwatch objwatch = new Stopwatch();

            for (int m = 0;m < 10; m++)

            {

                objwatch.Reset();

                objwatch.Start();

                for (int l = 0; l < 1000; l++)

                {

                    //another Method

                    PointToAddFunction p = delegate(int x, int y)

                   {

                       return x + y;

                   };

                    int z = p.Invoke(23, 45);

                  

                }

                objwatch.Stop();

                Console.WriteLine(objwatch.ElapsedTicks.ToString());

            }

            Console.ReadLine();

        }

        static int Add(int num1, int num2)

        {

            return num1 + num2;

        }

    }

}

Output is :  Recording For Anony Methods(Elapsing Time)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Diagnostics;

namespace AnonymousMethodsandDelegates

{

    class Program

    {

        delegate int PointToAddFunction(int num1, int num2);

        static void Main(string[] args)

        {

            Stopwatch objwatch = new Stopwatch();       

            for (int m = 0;m < 10; m++)

            {

                objwatch.Reset();

                objwatch.Start();

                for (int l = 0; l < 1000; l++)

                {

                    //another Method

                    PointToAddFunction p = Add;

                    int z = p.Invoke(23, 45);

                  

                }

                objwatch.Stop();

                Console.WriteLine(objwatch.ElapsedTicks.ToString());

            }

            Console.ReadLine();

        }

        static int Add(int num1, int num2)

        {

            return num1 + num2;

        }

    }

}

Recording for Named Delegates(Elapsing Time) : 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleLambda

{

    class Program

    {

        delegate double CalArePointer(int r);

       static   CalArePointer cpointer = CalculateArea;

        static void Main(string[] args)

        {

            double area = cpointer.Invoke(23);

            Console.WriteLine("Area of the Circle is : " + area);

            Console.ReadLine();

        }

        static double CalculateArea(int r)

        {

            return 3.14 * r * r;

        }

    }

   

}

  -------------------------xxxxxx Or  xxxx----------------------------------------------

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleLambda

{

    class Program

    {

        delegate double CalArePointer(int r);

     

        static void Main(string[] args)

        {

            CalArePointer cpointer = new CalArePointer(delegate(int r)

                   {

                       return 3.14 * r * r;

                   }

           );

            double area = cpointer(20);

            Console.WriteLine("Area of the Circle is : " + area);

            Console.ReadLine();

        }

      

    }

   

}

By using Lambda Expressions :

CalArePointer cpointer = r => 3.14 * r * r;           

            double area = cpointer(20);

            Console.WriteLine("Area of the Circle is : " + area);

Using Lambda Expressions+Functions :

Func<double, double> cpointer = r => 3.14 * r * r;

            double area = cpointer(20);

            Console.WriteLine("Area of the Circle is : " + area);

Using Action:

Action<string> Myaction = y => Console.WriteLine(y);

            Myaction("Welcome");

Using Predicates :

Predicate<string> checkgreaterthan5 = x => x.Length > 5;

            List<string> ostring = new List<string>();

            ostring.Add("Mohan");

            ostring.Add("Venkat");

            string str = ostring.Find(checkgreaterthan5);

            Console.WriteLine(str);

Expression Trees :

   Coding for  (23+56)-(40+20)

BinaryExpression b1 = Expression.MakeBinary(ExpressionType.Add,

                                                      Expression.Constant(23), Expression.Constant(56));

            BinaryExpression b2 = Expression.MakeBinary(ExpressionType.Add,

                                       Expression.Constant(40), Expression.Constant(20));

            BinaryExpression b3 = Expression.MakeBinary(ExpressionType.Subtract, b1, b2);

          int result=  Expression.Lambda<Func<int>>(b3).Compile()();

          Console.WriteLine("Result is : " + result);