USE lambda expression

 

        static void Main(string[] args)        {            #region "Building a List of Customers"             List<Customer> custList = new List<Customer>()                    {new Customer()                           { CustomerId = 1,                             FirstName="Bilbo",                             LastName = "Baggins",                              SalesTotal=10.0M,                            EmailAddress = "[e-mail]"                            },                     new Customer()                           { CustomerId = 2,                             FirstName="Frodo",                             LastName = "Baggins",                                SalesTotal=10.0M,                            EmailAddress = "[e-mail]"},                     new Customer()                           { CustomerId = 3,                             FirstName="Samwise",                             LastName = "Gamgee",                                SalesTotal=10.0M,                            EmailAddress = "[e-mail]"},                     new Customer()                           { CustomerId = 4,                             FirstName="Rosie",                             LastName = "Cotton",                                SalesTotal=10.0M,                            EmailAddress = "[e-mail]"}};             #endregion             #region "Lambda Expressions: Finding an Item in a Generic List"            //way1:loop list and compare            Customer foundCustomer = null;            foreach (var c in custList)            {                if (c.CustomerId == 4)                {                    foundCustomer = c;                    break;                }            }            Console.WriteLine(foundCustomer);            //way2 :LINQ            foundCustomer = null;            var query = from c in custList                        where c.CustomerId == 4                        select c;            foundCustomer = query.FirstOrDefault();            Console.WriteLine(foundCustomer);             //way3: anoymous method            foundCustomer = custList.Find(delegate(Customer c)            {                return c.CustomerId == 4;            });            //way4:lambda expression            foundCustomer = custList.FirstOrDefault<Customer>(c => c.CustomerId == 4);            foundCustomer = custList.FirstOrDefault<Customer>(c =>            {                return c.CustomerId == 4;            });             foundCustomer = custList.FirstOrDefault<Customer>((Customer c) => c.CustomerId == 4);            foundCustomer = custList.FirstOrDefault<Customer>((Customer c) =>            {                return c.CustomerId == 4;            });            foundCustomer = custList.Find(c => c.CustomerId == 4);             //Lambda Expressions: Predicate Delegates            //[ a predicate is “a function which returns a Boolean value”.]             var target = Array.Find<Customer>(custList.ToArray(), c => c.LastName.StartsWith("K"));            //Lambda Expressions: Action Delegates            //an action delegate encapsulates a method that performs an action and has no return value. It takes up to four parameters (and this number is increased in .NET 4.0             custList.ForEach(c => Console.WriteLine(c));             //Lambda Expressions: Func Delegates            //A Func delegate encapsulates a method that returns a value.             //It takes up to four parameters (and this number is increased in .NET 4.0) plus the return value.            var total = custList.Sum(c => c.SalesTotal);             //Lambdas: Aggregating Strings            /*The Select method first selects the email address for each customer.              * The Aggregate method then appends the email addresses together.             * And this code correctly handles the '”;” so you don’t have to think about it*/            IEnumerable<string> email = custList.Select(c => c.EmailAddress);            string m = email.Aggregate((items,item)=>items+";" +item);            string m2=custList.Select(c => c.EmailAddress)  .Aggregate((items, item) => items + "; " + item);             //Lambda Expressions: Finding Differences in Two Lists            /*             * To compare items in two lists and find which items in one list are not in the other.             * For example: {1, 2, 3}, {2, 3, 4}. {1} is only in the first list.             * To display the contents of the resulting set.             */            List<int> list1 = new List<int>() { 1, 6, 8 };            List<int> list2 = new List<int>() { 2, 6 };            /*             This is a Func delegate which returns an IEnumerable<int>.              * There are no arguments passed into the function, hence the empty parenthesis ().             * The => is the lambda operator. The remaining code uses the Except method of the list to find the items              * not in the second list.             */            Func<IEnumerable<int>> exceptionFunction = () => list1.Except(list2);            //The following lambda expression displays the resulting items            /*             * This one is an Action delegate that takes no parameters.              * It first takes the IEnumerable result from the exceptionFunction,             * converts it to a list, then writes each item to the Debug window             */            Action displayList = () => exceptionFunction().ToList().ForEach(i => Console.WriteLine(i));            displayList(); // Result 1,8              Console.ReadLine();               #endregion        }