Csharp/CSharp Tutorial/LINQ/select new

Constructor new object with select statement

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class Contact {
    public int Id;
    public string Name;
    public static void PublishContacts(Contact[] contacts) {
        foreach (Contact c in contacts)
            Console.WriteLine("Contact Id: {0} Contact: {1}", c.Id, c.Name);
    }
}

public class Employee {
    public int id;
    public string firstName;
    public string lastName;
    public static ArrayList GetEmployees() {
        ArrayList al = new ArrayList();
        al.Add(new Employee { id = 1, firstName = "J", lastName = "R" });
        al.Add(new Employee { id = 2, firstName = "W", lastName = "G" });
        al.Add(new Employee { id = 3, firstName = "A", lastName = "H" });
        return (al);
    }
}
public class MainClass {
    public static void Main() {
        ArrayList alEmployees = Employee.GetEmployees();
        Contact[] contacts = alEmployees
            .Cast<Employee>()
            .Select(e => new Contact {
                Id = e.id,
                Name = string.Format("{0} {1}", e.firstName, e.lastName)
            })
            .ToArray<Contact>();
        Contact.PublishContacts(contacts);
    }
}

Partitions an array of words into groups according to the first letter of each word.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
    public static void Main() {
        string[] words = { "b", "c", "a", "ba", "ae", "ch" };
        var wordGroups =
            from w in words
            group w by w[0] into g
            select new { FirstLetter = g.Key, Words = g };
        foreach (var g in wordGroups) {
            Console.WriteLine("Words that start with the letter "{0}":", g.FirstLetter);
            foreach (var w in g.Words) {
                Console.WriteLine(w);
            }
        }
    }
}

Query a List or objects and create new objects

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Reflection;
using System.Linq;
using System.Xml;
using System.Xml.Linq;
class Employee {
    int _id;
    int _idRole;
    string _lastName;
    string _firstName;
    public int ID {
        get { return _id; }
        set { _id = value; }
    }
    public int IDRole {
        get { return _idRole; }
        set { _idRole = value; }
    }
    public string LastName {
        get { return _lastName; }
        set { _lastName = value; }
    }
    public string FirstName {
        get { return _firstName; }
        set { _firstName = value; }
    }
}
class Role {
    int _id;
    string role;
    public int ID {
        get { return _id; }
        set { _id = value; }
    }
    public string Role {
        get { return role; }
        set { role = value; }
    }
}
class Program {
    static void Main(string[] args) {
        List<Employee> people = new List<Employee> {
               new Employee { ID = 1, IDRole = 1, LastName = "A", FirstName = "B"},
               new Employee { ID = 2, IDRole = 2, LastName = "G", FirstName = "T"}
            };
        List<Role> roles = new List<Role> {
              new Role  { ID = 1, Role = "Manager" },
              new Role  { ID = 2, Role = "Developer" }
            };
        var query = from p in people
                    where p.ID == 1
                    select new { p.FirstName, p.LastName };
    }
}

select new clause

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using System.Reflection;
public class MainClass{
   public static void Main(){
            var q = from m in typeof(int).GetMethods()
                    orderby m.Name
                    group m by m.Name into gb
                    select new {Name = gb.Key};
   }
}