LINQ to Objects Demo

Using the Code

1. Define the Person class that includes the ID, Name, and Age properties.

class Person 
{ 
    public Person(int id, string name, int age) 
    { 
        this.id = id; 
        this.name = name; 
        this.age = age; 
    } 
 
 
    private int id; 
 
 
    /// <summary> 
    /// Person ID 
    /// </summary> 
    public int PersonID 
    { 
        get { return this.id; } 
        set { this.id = value; } 
    } 
 
 
    private string name; 
 
 
    /// <summary> 
    /// Person name 
    /// </summary> 
    public string Name 
    { 
        get { return this.name; } 
        set { this.name = value; } 
    } 
 
 
    private int age; 
 
 
    /// <summary> 
    /// Age that ranges from 1 to 100 
    /// </summary> 
    public int Age 
    { 
        get { return this.age; } 
        set 
        { 
            if (value > 0 && value <= 100) 
                this.age = value; 
            else 
                throw new Exception("Age is out of scope [1,100]"); 
        } 
    } 
} 
 
2. Build a list of Person to be used as the data source.

       ///////////////////////////////////////////////////////////////////// 
       // Build the Person list that serves as the data source. 
       // 
       List<Person> persons = new List<Person>(); 
 
 
       persons.Add(new Person(1, "Alexander David", 20)); 
       persons.Add(new Person(2, "Aziz Hassouneh", 18)); 
       persons.Add(new Person(3, "Guido Pica", 20)); 
       persons.Add(new Person(4, "Chris Preston", 19)); 
       persons.Add(new Person(5, "Jorgen Rahgek", 20)); 
       persons.Add(new Person(6, "Todd Rowe", 18)); 
       persons.Add(new Person(7, "SPeter addow", 22)); 
       persons.Add(new Person(8, "Markus Breyer", 19)); 
       persons.Add(new Person(9, "Scott Brown", 20)); 
3. Use Linq to perform the query operation.

       ///////////////////////////////////////////////////////////////////// 
       // Query a person in the data source. 
       // 
       var Todd = (from p in persons 
                   where p.Name == "Todd Rowe" 
                    select p).First(); 
       // [-or-] 
       // Use extension method + lambda expression directly 
       //var Todd = persons.Where(p => p.Name == "Todd Rowe").First(); 
 
 
       Console.WriteLine("Todd Rowe's age is {0}", Todd.Age); 
4. Use Linq to perform the Update operation.

///////////////////////////////////////////////////////////////////// 
// Perform the Update operation on the person's age. 
// 
Todd.Age = 21; 
Console.WriteLine("Todd Rowe's age is updated to {0}", (from p in persons 
                                                        where p.Name == "Todd Rowe" 
                                                    select p).First().Age); 
5. Use Linq to perform the Order operation.

      ///////////////////////////////////////////////////////////////////// 
      // Sort the data in the data source. 
      // Order the persons by age 
      var query1 = from p in persons 
                   orderby p.Age 
                   select p; 
 
 
      Console.WriteLine("ID\tName\t\tAge"); 
 
 
      foreach (Person p in query1.ToList<Person>()) 
      { 
          Console.WriteLine("{0}\t{1}\t\t{2}", p.PersonID, p.Name, p.Age); 
      } 
6. Use Linq to perform the Max, Min, Average queries.

       ///////////////////////////////////////////////////////////////////// 
       // Print the average, max, min age of the persons. 
       // 
       double avgAge = (from p in persons 
                        select p.Age).Average(); 
       Console.WriteLine("The average age of the persons is {0:f2}", avgAge); 
 
 
       double maxAge = (from p in persons 
                        select p.Age).Max(); 
       Console.WriteLine("The maximum age of the persons is {0}", maxAge); 
 
 
       double minAge = (from p in persons 
                        select p.Age).Min(); 
       Console.WriteLine("The minimum age of the persons is {0}", minAge); 
7. Use Linq to count the Person whose age is larger than 20

       ///////////////////////////////////////////////////////////////////// 
       // Count the persons who age is larger than 20 
       // 
       var query2 = from p in persons 
                    where p.Age > 20 
                    select p; 
 
 
       int count = query2.Count(); 
       Console.WriteLine("{0} persons are older than 20:", count); 
       for (int i = 0; i < count; i++) 
       { 
           Console.WriteLine(query2.ElementAt(i).Name); 
       }