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In Below example we will read xml document in c# using linq. First i have created a xml file with below content


< ?xml version="1.0" encoding="utf-8" ?>
< websites xmlns="URN:websitename">
< websitename>getproductprice.com< /websitename>
< websitename>interviewqsn.com< /websitename>
< /websites>


To read above xml file we will write below code and name of ABOV file is websites.xml

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
namespace LinqExample
{
class websitename
{
STATIC void Main(string[] args)
{
var doc = XDocument.Load("websites.xml");
var QUERY = from x in doc.Descendants("{urn:websitename}websitename")
select x;
foreach (var item in query)
{
Console.WriteLine(item);
}
}
}
}

Below code will helps you to understand that how linq is apply to datatable in asp.net:-
using LINQ
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Data;
using System.Data.SqlClient;

namespace LinQSamples
{
class Program
{
static void Main(string[] args)
{
DtMethod();
}
public static DataTable createDataTable()
{
DataTable DT = new DataTable();
dt.Columns.Add("EMPID", typeof(INT));
dt.Columns.Add("empname", typeof(string));
dt.Columns.Add("salary", typeof(int));
dt.Rows.Add(1, "Adam", 10000);
dt.Rows.Add(2, "Sutro", 1000);
dt.Rows.Add(3, "Ricky", 3000);
dt.Rows.Add(4, "Martin", 66000);
dt.Rows.Add(5, "Mike", 5000);
dt.Rows.Add(6, "Jonson", 100);
dt.Rows.Add(7, "Michel", 4500);
dt.Rows.Add(8, "John", 7000);
return dt;
}
public static void DtMethod()
{
DataTable dtTable = createDataTable();
//SELECT Statement using LINQ is given below
var SelectQuery = from SQ in dtTable.AsEnumerable() select sq;
console.WriteLine(" nResult for select statement");
Console.WriteLine("-------------------");
foreach (DataRow Query in SelectQuery)
{
Console.WriteLine("{0} t{1} t{2}", Query.ItemArray);
}
///Below Statement is with where condition(empid =100)
var querySalarySum = from qs in dtTable.AsEnumerable()
where qs.Field("empid") == 100
select qs;
Console.WriteLine("EmpId t Name t t Salary");
foreach (DataRow dr in querySalarySum)
{
Console.WriteLine("{0} t{1} t{2}",
dr.Field("empid"),
dr.Field("empname"),
dr.Field("salary"));
}
}
}
}

Below code is USED to sort string ARRAY using LINQ:-
static void Main(string[] args)
{
string[] data = { "Adam", "Sutro", "Lilly" };
List sortData = NEW List(data);
sortData.Sort((string a, string b) =&GT;
{
return a.CompareTo(b);
}
);
Console.WriteLine(string.Join(",", sortData.ToArray()));
Console.Read();
}

Below program first create INT array and then apply QUERY on that array and sort with the help of linq
using System;
using System.Linq;
class SortArrayLinqProgram
{
STATIC void Main()
{
int[] array1 = { 5, 4, 1, 2, 3 };
var query = from element in array1
orderby element
select element;
int[] array2 = query.ToArray();
foreach (int value in array2)
{
Console.WriteLine(value);
}
}
}

Below code helps US to get element in array is multiple of 3 or not if it is value return is true else false

static void Main(STRING[] args)
{
//below is the array contains elements
int[] arrayno = { 12, 33, 24, 90, 99, 42, 75 };
BOOL CheckMultiple = CheckElement(arrayno, 3);
}

//function which return either true or false
private static bool CheckElement(int[] arrayno, int divisor)
{
bool CheckMultiple = arrayno.All(number => number % divisor == 0);
return CheckMultiple;
}

Single() vs SingleOrDefault() vs First() vs FirstOrDefault() in LINQ Query
Below are the 3 MAIN difference between Single() vs SingleOrDefault() vs First() vs FirstOrDefault()

Defination

Exception thrown

When to Use

How to do ARRAY SLICING Using LINQ?
To understand this we will take an array of 10 elements and out of which we need to return FIVE of them, with the intention to return the rest of them on demand. And it is known as pagination and it is achieved by using two mainly methods of LINQ that are Skip() and Take(). So import LINQ and use two of these methods as in below given example:-


var objElements=new string[] {"E1","E2","E3","E4","E5","E6","E7","E8","E9","E10"};
var objSliced=objElements.Skip(0).Take(5);
foreach (var obj in objSliced)
Console.WriteLine(obj);



In above CODE we PASS number of element we want to skip is pass to Skip() method. And this will turns out to be starting index as we put 0 with Skip methods. And in second method is Take() here we pass the number of elements which we want to include in Take() method. And this operation returns a new IEnumerable that we can enumerate.

Important aspects of Query Operators in LINQ?
There are lots of query-patterns which explain how should write query on data by using LINQ. And these patterns are desgined by help of extension methods. And these query patterns are KNOWN as Query Operators. LINQ query operators can be categorized into below ways.
(1)Join Operators:-Join, GroupJoin
(2)Projection Operations:-Select
(3)Sorting Operators:-OrderBy, OrderByDescending, ThenBy, ThenByDescending, REVERSE
(4)Grouping Operators:-GroupBy, ToLookUp
(5)Filtering Operators:-OfType, Where
(6)Aggregation:-Aggregate, AVERAGE, Count, LonCount, Max, Min, Sum
(7)Set Operators:-Distinct,Except,Intersect,Union
(8)Conversions:-AsEnumerable, AsQueryable, Cast, OfType, TOARRAY, ToDictionary, ToList,ToLookup
(9)Partition Operators:-Skip, SkipWhile, Take, TakeWhile