Basic of LINQ

 

The acronym LINQ is for Language Integrated Query. Microsoft’s query language is fully integrated and offers easy data access from in-memory objects, databases, XML documents and many more. It is through a set of extensions, LINQ ably integrate queries in C# and Visual Basic.

 

Basic Example of LINQ 

 

using System;

using System.Linq;

class Program

{

static void Main()

{

string[] words = {"hello", "wonderful", "LINQ", "beautiful", "world"};

var shortWords = from word in words

where word.Length <= 5

select word;

foreach (var word in shortWords)

{

Console.WriteLine(word);

}

Console.ReadLine();

}

}

 

Output :

hello

LINQ

world

 

The types of LINQ :-

LINQ to Objects

LINQ to XML(XLINQ)

LINQ to DataSet

LINQ to SQL (DLINQ)

LINQ to Entities

 

 

 

 

 

 

 

 

 

 

 

 

LINQ to SQL Example

 

using System;

using System.Linq;

namespace LINQtoSQL

{

class LinqToSQLCRUD

{

static void Main(string[] args)

{

string connectString = System.Configuration.ConfigurationManager.ConnectionStrings ["LinqToSQLDBConnectionString"].ToString();

LinqToSQLDataContext db = new LinqToSQLDataContext(connectString);

//Create new Employee

Employee newEmployee = new Employee();

newEmployee.Name = "ABC";

newEmployee.Email = "abc@xyz.com";

newEmployee.ContactNo = "1234567890";

newEmployee.DepartmentId = 3;

newEmployee.Address = "India";

//Add new Employee to database

db.Employees.InsertOnSubmit(newEmployee);

//Save changes to Database.

db.SubmitChanges();

//Get new Inserted Employee

Employee insertedEmployee = db.Employees.FirstOrDefault(e =>e.Name.Equals("Michael"));

Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}, Address = {4}",

insertedEmployee.EmployeeId, insertedEmployee.Name, insertedEmployee.Email,

insertedEmployee.ContactNo, insertedEmployee.Address);

Console.WriteLine("\nPress any key to continue.");

Console.ReadKey();

}

}

}

using System;

using System.Linq;

namespace LINQtoSQL

{

class LinqToSQLCRUD

{

static void Main(string[] args)

{

string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();

LinqToSQLDataContext db = new LinqToSQLDataContext(connectString);

//Get Employee for update

Employee employee = db.Employees.FirstOrDefault(e =>e.Name.Equals("Michael"));

newEmployee.Name = "ABC";

newEmployee.Email = "abc@xyz.com";

newEmployee.ContactNo = "9954567890";

newEmployee.DepartmentId = 3;

newEmployee.Address = "India-Delhi";

//Save changes to Database.

db.SubmitChanges();

//Get Updated Employee

Employee updatedEmployee = db.Employees.FirstOrDefault(e =>e.Name.Equals("George Michael"));

Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}, Address = {4}",

updatedEmployee.EmployeeId, updatedEmployee.Name, updatedEmployee.Email,

updatedEmployee.ContactNo, updatedEmployee.Address);

Console.WriteLine("\nPress any key to continue.");

Console.ReadKey();

}

}

}

using System;

using System.Linq;

namespace LINQtoSQL

{

class LinqToSQLCRUD

{

static void Main(string[] args)

{

string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();

LinqToSQLDataContext db = newLinqToSQLDataContext(connectString);

//Get Employee to Delete

Employee deleteEmployee = db.Employees.FirstOrDefault(e =>e.Name.Equals("ABC"));

//Delete Employee

db.Employees.DeleteOnSubmit(deleteEmployee);

//Save changes to Database.

db.SubmitChanges();

//Get All Employee from Database

var employeeList = db.Employees;

foreach (Employee employee in employeeList)

{

Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}",

employee.EmployeeId, employee.Name, employee.Email, employee.ContactNo);

}

Console.WriteLine("\nPress any key to continue.");

Console.ReadKey();

}

}

}

 

 

 

 

 

 

 

 

 

 

 

LINQ to Object Example

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace LINQtoObjects

{

class Program

{

static void Main(string[] args)

{

string[] tools = { "A", "B", "C", "D", "E","F" };

var list = from t in tools

select t;

StringBuilder sb = new StringBuilder();

foreach (string s in list)

{

sb.Append(s + Environment.NewLine);

}

Console.WriteLine(sb.ToString(), "Tools");

Console.ReadLine();

}

}

}

 

 

 

 

 

 

 

 

 

 

LINQ to XML Example

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Xml.Linq;

namespace LINQtoXML

{

class ExampleOfXML

{

static void Main(string[] args)

{

string myXML = @"<Departments>

<Department>Account</Department>

<Department>IT</Department>

<Department>Sales</Department>

<Department>Marketing</Department>

</Departments>";

XDocument xdoc = new XDocument();

xdoc = XDocument.Parse(myXML);

var result = xdoc.Element("Departments").Descendants();

foreach (XElement item in result)

{

Console.WriteLine("Department Name - " + item.Value);

}

Console.WriteLine("\nPress any key to continue.");

Console.ReadKey();

}

}

}