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why are use LINQ Where Clause in LINQ?

Ethan Karla 753 24-Sep-2021

How to use LINQ Where Clause Filtering Operator in SQL data or normal data?

linq c#  ado.net  linq 
Updated on 24-Sep-2021
Ethan Karla

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2 Answers

Ravi Vishwakarma

Ravi Vishwakarma

27-Sep-2021

In LINQ where clauses are used for filtering the collection or SQL data. In another word where clauses help to filter the condition-based data for collection or SQL server.

Syntax 

datatype variable = from object in collections
                   where condition,
                   where condition
                   select object;

datatype variable = collection.where( lambda variable => condition );

Example 

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
 public static void Main()
 {
  List<Student> students = new List<Student>()
  {
  new Student() { StudentId = 1, Name = 'Asu', Marks = 500 },
  new Student() { StudentId = 2, Name = 'Shyam', Marks = 300 },
  new Student() { StudentId = 3, Name = 'Shriyam', Marks = 400 },
  new Student() { StudentId = 4, Name = 'Sunny', Marks = 550 },
  new Student() { StudentId = 5, Name = 'Ram', Marks = 600 },
  new Student() { StudentId = 6, Name = 'Krishna', Marks = 700 },
  new Student() { StudentId = 7, Name = 'Anupam', Marks = 550 }
  };

  // select projection using first sysntax

  var result1= from student in students 
     where student.Marks > 300 && student.Marks < 700
     select student ;

  Console.WriteLine('Using First Syntax :\n');
  result1.ToList().ForEach(item => Console.WriteLine('StudentName is {0}, ID is {1}, and Marks is {2}', item.Name, item.StudentId, item.Marks) );

  var result2 = from student in students
       where student.Marks > 300
       where student.Marks < 700
       select new {Name =student.Name,ID = student.StudentId,Marks = student.Marks };

  Console.WriteLine('\nUsing Second Syntax :\n');
  result2.ToList().ForEach(item => Console.WriteLine('StudentName is {0}, ID is {1}, and Marks is {2}', item.Name, item.ID, item.Marks) );

  var result3 = students.Where( student => student.StudentId < 5);

  Console.WriteLine('\nUsing where method Syntax :\n');
  result3.ToList().ForEach(item => Console.WriteLine('StudentName is {0}, ID is {1}, and Marks is {2}', item.Name, item.StudentId, item.Marks) );

  Console.ReadLine();
 }
}

class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
}

Output 

Using First Syntax :
StudentName is Asu, ID is 1, and Marks is 500
StudentName is Shriyam, ID is 3, and Marks is 400
StudentName is Sunny, ID is 4, and Marks is 550
StudentName is Ram, ID is 5, and Marks is 600
StudentName is Anupam, ID is 7, and Marks is 550
Using Second Syntax :
StudentName is Asu, ID is 1, and Marks is 500
StudentName is Shriyam, ID is 3, and Marks is 400
StudentName is Sunny, ID is 4, and Marks is 550
StudentName is Ram, ID is 5, and Marks is 600
StudentName is Anupam, ID is 7, and Marks is 550
Using where method Syntax :
StudentName is Asu, ID is 1, and Marks is 500
StudentName is Shyam, ID is 2, and Marks is 300
StudentName is Shriyam, ID is 3, and Marks is 400
StudentName is Sunny, ID is 4, and Marks is 550


Ravi Vishwakarma

Ravi Vishwakarma

26-Sep-2021

In LINQ where clauses are used for filtering the collection or SQL data. In another word where clauses help to filter the condition-based data for collection or SQL server.

Syntax 

datatype variable = from object in collections
                    where condition,
                    where condition
                    select object;

datatype variable = collection.where( lambda variable => condition );


Example 

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
 public static void Main()
 {
  List<Student> students = new List<Student>()
  {
  new Student() { StudentId = 1, Name = 'Asu', Marks = 500 },
  new Student() { StudentId = 2, Name = 'Shyam', Marks = 300 },
  new Student() { StudentId = 3, Name = 'Shriyam', Marks = 400 },
  new Student() { StudentId = 4, Name = 'Sunny', Marks = 550 },
  new Student() { StudentId = 5, Name = 'Ram', Marks = 600 },
  new Student() { StudentId = 6, Name = 'Krishna', Marks = 700 },
  new Student() { StudentId = 7, Name = 'Anupam', Marks = 550 }
  };

  // select projection using first sysntax
  var result1= from student in students 
               where student.Marks > 300 && student.Marks < 700
               select student ;
  Console.WriteLine('Using First Syntax :\n');
  result1.ToList().ForEach(item => Console.WriteLine('StudentName is {0}, ID is {1}, and Marks is {2}', item.Name, item.StudentId, item.Marks) );

  var result2 = from student in students
                where student.Marks > 300
                where student.Marks < 700
                select new {Name =student.Name,ID = student.StudentId,Marks = student.Marks };

  Console.WriteLine('\nUsing Second Syntax :\n');
  result2.ToList().ForEach(item => Console.WriteLine('StudentName is {0}, ID is {1}, and Marks is {2}', item.Name, item.ID, item.Marks) );

  var result3 = students.Where( student => student.StudentId < 5);
  Console.WriteLine('\nUsing where method Syntax :\n');
  result3.ToList().ForEach(item => Console.WriteLine('StudentName is {0}, ID is {1}, and Marks is {2}', item.Name, item.StudentId, item.Marks) );

  Console.ReadLine();
 }
}

class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
}

Output 

Using First Syntax :
StudentName is Asu, ID is 1, and Marks is 500
StudentName is Shriyam, ID is 3, and Marks is 400
StudentName is Sunny, ID is 4, and Marks is 550
StudentName is Ram, ID is 5, and Marks is 600
StudentName is Anupam, ID is 7, and Marks is 550
Using Second Syntax :
StudentName is Asu, ID is 1, and Marks is 500
StudentName is Shriyam, ID is 3, and Marks is 400
StudentName is Sunny, ID is 4, and Marks is 550
StudentName is Ram, ID is 5, and Marks is 600
StudentName is Anupam, ID is 7, and Marks is 550
Using where method Syntax :
StudentName is Asu, ID is 1, and Marks is 500
StudentName is Shyam, ID is 2, and Marks is 300
StudentName is Shriyam, ID is 3, and Marks is 400
StudentName is Sunny, ID is 4, and Marks is 550


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