PROWAREtech
.NET: Language Integrated Query (LINQ) - Page 3
Count Operator, Where and OrderByDescending.
The Count() Operator
Count() returns the record count.
using System;
using System.Collections.Generic;
using System.Linq;
namespace LinqExample
{
[Serializable]
public class Person : IComparable<Person>, IFormattable
{
public string LastName { get; set; }
public string FirstName { get; set; }
public int Age { get; set; }
public string[] Cars { get; private set; }
public Person(string LastName = null, string FirstName = null, int Age = 0, IEnumerable<string> Cars = null)
{
this.LastName = LastName;
this.FirstName = FirstName;
this.Age = Age;
List<string> cars = new List<string>();
foreach (string car in Cars)
{
cars.Add(car);
}
this.Cars = cars.ToArray();
}
public int CompareTo(Person person)
{
if (person == null)
throw new ArgumentNullException("person");
return LastName.CompareTo(person.LastName);
}
public override string ToString()
{
return LastName + ", " + FirstName;
}
public string ToString(string format)
{
return ToString(format, null);
}
public string ToString(string format, IFormatProvider FormatProvider)
{
switch (format)
{
case null:
case "N": // return full name
return ToString();
case "L": // return last name
return LastName;
case "F": // return first name
return FirstName;
case "A": // return all information
return ToString() + " - " + Age.ToString();
default:
throw new FormatException("Format " + format + " unsupported");
}
}
}
public static class Classroom
{
private static List<Person> students;
public static IList<Person> GetAttendance()
{
if (students == null)
{
students = new List<Person>();
students.Add(new Person("Holman", "Kaylee", 35, new string[] { "Civic", "Smart Car" }));
students.Add(new Person("Crabtree", "Glenn", 30, new string[] { "Element" }));
students.Add(new Person("Kellerman", "Calandra", 30, new string[] { "F150", "Civic" }));
students.Add(new Person("Chairez", "Judy", 27, new string[] { "Outback", "Element" }));
students.Add(new Person("Santore", "Cari", 42, new string[] { "F250" }));
students.Add(new Person("Barnaby", "Emelda", 27, new string[] { "Cayenne" }));
students.Add(new Person("Beeler", "Rufina", 22, new string[] { "320i", "911" }));
students.Add(new Person("Barreiro", "Jessia", 31, new string[] { "WRX", "Civic", "Ridgeline" }));
students.Add(new Person("Kummer", "Bebe", 30, new string[] { "F150" }));
students.Add(new Person("Sexson", "Aleida", 25, new string[] { "Outback" }));
students.Add(new Person("Ansell", "Freida", 44, new string[] { "Element" }));
students.Add(new Person("Eriksson", "Jae", 49, new string[] { "Pilot", "Accord" }));
}
return students;
}
}
class Program
{
static void Main()
{
var countQuery = from p in Classroom.GetAttendance()
where p.Cars.Count() >= 2
orderby p.Cars.Count() descending
select p;
foreach (Person obj in countQuery)
{
Console.WriteLine("{0:A}; cars: {1}", obj, obj.Cars.Count());
}
}
}
}
Barreiro, Jessia - 31; cars: 3 Holman, Kaylee - 35; cars: 2 Kellerman, Calandra - 30; cars: 2 Chairez, Judy - 27; cars: 2 Beeler, Rufina - 22; cars: 2 Eriksson, Jae - 49; cars: 2
Using Lambda with LINQ Methods Where() and OrderByDescending()
using System;
using System.Collections.Generic;
using System.Linq;
namespace LinqExample
{
[Serializable]
public class Person : IComparable<Person>, IFormattable
{
public string LastName { get; set; }
public string FirstName { get; set; }
public int Age { get; set; }
public string[] Cars { get; private set; }
public Person(string LastName = null, string FirstName = null, int Age = 0, IEnumerable<string> Cars = null)
{
this.LastName = LastName;
this.FirstName = FirstName;
this.Age = Age;
List<string> cars = new List<string>();
foreach (string car in Cars)
{
cars.Add(car);
}
this.Cars = cars.ToArray();
}
public int CompareTo(Person person)
{
if (person == null)
throw new ArgumentNullException("person");
return LastName.CompareTo(person.LastName);
}
public override string ToString()
{
return LastName + ", " + FirstName;
}
public string ToString(string format)
{
return ToString(format, null);
}
public string ToString(string format, IFormatProvider FormatProvider)
{
switch (format)
{
case null:
case "N": // return full name
return ToString();
case "L": // return last name
return LastName;
case "F": // return first name
return FirstName;
case "A": // return all information
return ToString() + " - " + Age.ToString();
default:
throw new FormatException("Format " + format + " unsupported");
}
}
}
public static class Classroom
{
private static List<Person> students;
public static IList<Person> GetAttendance()
{
if (students == null)
{
students = new List<Person>();
students.Add(new Person("Holman", "Kaylee", 35, new string[] { "Civic", "Smart Car" }));
students.Add(new Person("Crabtree", "Glenn", 30, new string[] { "Element" }));
students.Add(new Person("Kellerman", "Calandra", 30, new string[] { "F150", "Civic" }));
students.Add(new Person("Chairez", "Judy", 27, new string[] { "Outback", "Element" }));
students.Add(new Person("Santore", "Cari", 42, new string[] { "F250" }));
students.Add(new Person("Barnaby", "Emelda", 27, new string[] { "Cayenne" }));
students.Add(new Person("Beeler", "Rufina", 22, new string[] { "320i", "911" }));
students.Add(new Person("Barreiro", "Jessia", 31, new string[] { "WRX", "Civic", "Ridgeline" }));
students.Add(new Person("Kummer", "Bebe", 30, new string[] { "F150" }));
students.Add(new Person("Sexson", "Aleida", 25, new string[] { "Outback" }));
students.Add(new Person("Ansell", "Freida", 44, new string[] { "Element" }));
students.Add(new Person("Eriksson", "Jae", 49, new string[] { "Pilot", "Accord" }));
}
return students;
}
}
class Program
{
static void Main()
{
var countQuery = Classroom.GetAttendance().Where(p => p.Cars.Count() >= 2).OrderByDescending(p => p.Cars.Count());
foreach (Person obj in countQuery)
{
Console.WriteLine("{0:A}; cars: {1}", obj, obj.Cars.Count());
}
}
}
}
Barreiro, Jessia - 31; cars: 3 Holman, Kaylee - 35; cars: 2 Kellerman, Calandra - 30; cars: 2 Chairez, Judy - 27; cars: 2 Beeler, Rufina - 22; cars: 2 Eriksson, Jae - 49; cars: 2
Comment
