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"));
}
}
}
}