The Knowledge Foundation

"Select" is a query operator , Select operator returns result of a given query.
LINQ uses "select" query operator in two type, "select" and "select new". Select operator filter the original object, it is reference to the original objects. "Select new" also is query operator, that returns result of anonymous type by creating new instance of the particular type.

We are going to discuss about implementation of select statement in various type and designs.

1) The example simple select statement.

using System;

using System.Collections.Generic;

using System.Data.SqlClient;

using System.Data.Sql;

using System.Data;

using System.Linq;

using System.Collections;

using System.Xml;

using System.Text;

using System.Xml.Linq;

using System.IO;

namespace ConsoleApplication1

{

class Program

{

static void Main(string[] args)

{

ArrayList myList = new ArrayList();

myList.Add (new student {name = "John1", roll = 121,age = 5});

myList.Add(new student { name = "John2", roll = 122, age = 6 });

myList.Add(new student { name = "John3", roll = 123, age = 7 });

myList.Add(new student { name = "John4", roll = 124, age = 8 });

myList.Add(new student { name = "John5", roll = 125, age = 9 });

myList.Add(new student { name = "John6", roll = 126, age = 10 });

myList.Add(new student { name = "John7", roll = 127, age = 11 });

myList.Add(new student { name = "John8", roll = 128, age = 17 });

myList.Add(new student { name = "John9", roll = 129, age = 18 });

myList.Add(new student { name = "John10", roll = 1210, age = 19 });

myList.Add(new student { name = "John11", roll = 1211, age = 20 });

var query = from student s in myList

select s;

foreach (student c in query)

{

Console.WriteLine("Name : " + c.name + "|Roll :" + c.roll + "| c.age:" + c.age);

}

Console.ReadLine();

}

public class student

{

public string name { get; set; }

public int roll { get; set; }

public int age { get; set; }

}

Output :

2)The example shows that , we can do some string operations in output , there are some inbuilt function is there to handle the sting operation or you can write your custom operation during the query writing.

namespace ConsoleApplication1

{

class Program

{

static void Main(string[] args)

{

ArrayList myList = new ArrayList();

myList.Add(new student { name = "John1", roll = 121, age = 5 });

myList.Add(new student { name = "John2", roll = 122, age = 6 });

myList.Add(new student { name = "John3", roll = 123, age = 7 });

myList.Add(new student { name = "John4", roll = 124, age = 8 });

myList.Add(new student { name = "John5", roll = 125, age = 9 });

myList.Add(new student { name = "John6", roll = 126, age = 10 });

myList.Add(new student { name = "John7", roll = 127, age = 11 });

myList.Add(new student { name = "John8", roll = 128, age = 12 });

myList.Add(new student { name = "John9", roll = 129, age = 13 });

myList.Add(new student { name = "John10", roll = 1210, age = 14 });

myList.Add(new student { name = "John11", roll = 1211, age = 15 });

var query = from student s in myList

select new {

name = s.name.ToUpper(),

roll = s.roll ,

age = s.age

};

Console.ReadKey();

}

}

Output :

public class student

{

public string name { get; set; }

public int roll { get; set; }

public int age { get; set; }

}

3)The example shows that , select statement can be calculated in the output. We can perform some calculation during the output results.

using System;