005 LINQ to XML

XML is well known format to hold data. It is widely accepted all over the world. Formatting XML data depend upon the node ,attribute, elements ect . You can easily access , modify node , attribute , elements through programming languages. LINQ to XML is it functionality of.Net framework to query and modify the XML in memory.  LINQ to XML increase the productivity, developer need to write less code and it is compact. To  implement LINQ to XML, you need to load XML in memory first, then only you can modify or query in the XML document. The advantage of these approaches is, the process is integrated with languages and very lightweight, during the compilation of program , checking is done over the query and modification. After the query or notification is over , now you can save the XML document to physical file and you can do the necessary work with memory  XML file.  System.Xml.Linq  is the namespace  is used for XML manipulation.

Below Example Show 
1)A Simple select query ,return list of student.
2)A Simple select query with where condition,return list of student whose marks greater than 15
3)A Simple select query with where condition,return list of student whose Roll is 14.



Example

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)

             {

               StringBuilder sb = new StringBuilder();

               sb.Append("");

               sb.Append("");

               sb.Append("John1");

               sb.Append("12");

               sb.Append("12.50");

               sb.Append("");

               sb.Append("");

               sb.Append("John2");

               sb.Append("13");

               sb.Append("13.50");

               sb.Append("");

               sb.Append("");

               sb.Append("John3");

               sb.Append("14");

               sb.Append("14.50");

               sb.Append("");

               sb.Append("");

               sb.Append("John4");

               sb.Append("14");

               sb.Append("14.50");

               sb.Append("");

               sb.Append("");

               sb.Append("John5");

               sb.Append("15");

               sb.Append("15.50");

               sb.Append("");

               sb.Append("");

               sb.Append("John6");

               sb.Append("16");

               sb.Append("16.50");

               sb.Append("");

               sb.Append("");

               sb.Append("John7");

               sb.Append("17");

               sb.Append("17.50");

               sb.Append("");
               sb.Append("");

       TextReader tr = new StringReader(sb.ToString());

       XDocument xdoc = XDocument.Load(tr);

       /******************LINQ to XML --Simple Select Query*******************/

       Console.WriteLine("*********************List of Student*******************");

       var lv1s = from lv1 in xdoc.Descendants("student")

                  select new

                  {

                  Name = lv1.Element("Name").Value,

                  Roll = lv1.Element("Roll").Value,

                  Marks = lv1.Element("Marks").Value

                 };

              foreach (var lv1 in lv1s)

              {

                 Console.WriteLine("Name = {0} , RollNumber = {1} ,Marks = {1} ",

                 lv1.Name, lv1.Roll, lv1.Marks);

              }

              Console.ReadKey();

        Console.WriteLine("*********************List of Student, Marks greated than 15***********");

            var lv1a = from lva in xdoc.Descendants("student")

                      where Convert.ToDecimal(lva.Element("Marks").Value) >= 15

                      select new

                      {

                         Name = lva.Element("Name").Value,

                         Roll = lva.Element("Roll").Value,

                         Marks = lva.Element("Marks").Value

                     };

             foreach (var lv1 in lv1a)

             {

                Console.WriteLine("Name = {0} , RollNumber = {1} ,Marks = {1} ",

                 lv1.Name, lv1.Roll, lv1.Marks);

             }

             Console.ReadKey();

Console.WriteLine("*********************List of Student, Filter by Roll=14***********");

          IEnumerable<XElement> stu = from el in xdoc.Elements("student")

          where (string)el.Element("Roll") == "14"

          select el;

           foreach (var stuElm in stu)

          {

               Console.WriteLine("Name = {0}", stuElm.Name);

          }

             Console.ReadKey();

         }

     }

}

Output :

*********************List of Student*******************

Name = John1 , RollNumber = 12 ,Marks = 12

Name = John2 , RollNumber = 13 ,Marks = 13

Name = John3 , RollNumber = 14 ,Marks = 14

Name = John4 , RollNumber = 14 ,Marks = 14

Name = John5 , RollNumber = 15 ,Marks = 15

Name = John6 , RollNumber = 16 ,Marks = 16

Name = John7 , RollNumber = 17 ,Marks = 17

*********************List of Student, Marks greated than 15***********

Name = John5 , RollNumber = 15 ,Marks = 15

Name = John6 , RollNumber = 16 ,Marks = 16

Name = John7 , RollNumber = 17 ,Marks = 17

*********************List of Student, Filter by Roll=14***********