/DelegatesEventsAndLambdas/4. Using Lambdas.cs

// ReSharper disable RedundantLambdaParameterType

/*

 *      This example demonstrates the use of a lambdas. Step through the test methods and see how they work.

 *      

 *      Terminology:

 *      

 *          1.  Lambda  -   A lambda expression is an anonymous function that can contain expressions and statements, 

 *                          and can be used to create delegates or expression tree types. All lambda expressions use 

 *                          the lambda operator =>, which is read as "goes to". The left side of the lambda operator 

 *                          specifies the input parameters (if any) and the right side holds the expression or statement 

 *                          block. The lambda expression [[ x => x * x ]] is read "x goes to x times x." 

 *          

 *      Observe:

 *      

 *          1.  The most long-winded form of a lambda expression goes like this:

 *                  

 *                  (explicitly-typed-parameter-list) => { statements }

 *                  

 *          2.  The compiler is smart enough to reduce this down to the bare necessities:

 *          

 *                  parameter-name => expression

 */





using System;

using NUnit.Framework;

using System.Linq;



namespace DelegatesAndLambdas

{

    [TestFixture]

    public class Lambdas

    {

        // Declaration

        public delegate void SimpleDelegate(double parm1);



        [Test]

        public void Use_a_simple_lambda_expression()

        {

            // Instantiation - anonymous method

            SimpleDelegate anon = delegate(double number) { Console.WriteLine(Math.Sqrt(number)); };



            // Instantiation - lambda, full syntax

            SimpleDelegate lambda1 = (double number) => Console.WriteLine(Math.Sqrt(number));



            // Instantiation - lambda, shorthand

            SimpleDelegate lambda2 = (number) => Console.WriteLine(Math.Sqrt(number));



            // Instantiation - lambda, concise

            SimpleDelegate lambda3 = number => Console.WriteLine(Math.Sqrt(number));



            // Invocation

            anon(49);

            lambda1(49);

            lambda2(49);

            lambda3(49);



        }



        [Test]

        public void Use_a_lamda_expression_that_returns_a_result()

        {

            // Instantiation - anonymous method

            Func<string, int> returnLengthAnon = delegate(string text) { return text.Length; };



            // Instantiation - lambda, full syntax

            Func<string, int> returnLengthLambda1 = (string text) => { return text.Length; };



            // Instantiation - lambda, shorthand

            Func<string, int> returnLengthLambda2 = (string text) => text.Length; 



            // Instantiation - lambda, concise

            Func<string, int> returnLengthLambda3 = text => text.Length;





            // Invocation

            Console.WriteLine(returnLengthAnon("Hello Anonymous World"));

            Console.WriteLine(returnLengthLambda1("Hello Lambda World"));

            Console.WriteLine(returnLengthLambda2("Hello Lambda World"));

            Console.WriteLine(returnLengthLambda3("Hello Lambda World"));

        }

        



    }

}