LINQ 05 Projection

A linq statement can project the properties of collection items into new items of a anonymous collection.

using System;

using System.Linq;

namespace pc.linq04

{

    class Person

    {

        public string FirstName { get; set; }

        public string LastName { get; set; }

        public Person(string FirstName, string LastName)

        {

            this.FirstName = FirstName;

            this.LastName = LastName;

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            var ppl = new Person[] { new Person("Pawel", "Chooch"),

                new Person("Magda", "Tyvoniuk"), new Person("Tomek","Chook"),

                new Person("Marin","Smartzic"), new Person("Jake","Tyvoniuk")};

            var result1 = from p in ppl

                          select new { FullName = $"{p.FirstName} {p.LastName}" };

            var result2 = ppl.Select(p => new { FullName = $"{p.FirstName} {p.LastName}" });

            Array.ForEach(result1.ToArray(), p => Console.Write(p.FullName+ ", "));

            Console.WriteLine();

            Array.ForEach(result2.ToArray(), p => Console.Write(p.FullName+ ", "));

            Console.WriteLine();

        }

    }

}

as you can see in both the expression and method based queries we take our person class and project each of it's instances into a new anonymous object that only has a FullName property.

Of course before we project our objects we can filter them

using System;

using System.Linq;

namespace pc.linq04

{

    class Person

    {

        public string FirstName { get; set; }

        public string LastName { get; set; }

        public Person(string FirstName, string LastName)

        {

            this.FirstName = FirstName;

            this.LastName = LastName;

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            var ppl = new Person[] { new Person("Pawel", "Chooch"),

                new Person("Magda", "Tyvoniuk"), new Person("Tomek","Chooch"),

                new Person("Marin","Smartzic"), new Person("Jake","Tyvoniuk")};

            var result1 = from p in ppl

                          where p.LastName == "Chooch"

                          select new { FullName = $"{p.FirstName} {p.LastName}" };

            var result2 = ppl.Where(p=> p.LastName == "Tyvoniuk")

                             .Select(p => new { FullName = $"{p.FirstName} {p.LastName}" });

            Array.ForEach(result1.ToArray(), p => Console.Write(p.FullName+ ", "));

            Console.WriteLine();

            Array.ForEach(result2.ToArray(), p => Console.Write(p.FullName+ ", "));

            Console.WriteLine();

        }

    }

}

in the above we use the where function to to filter our data before projecting it.