Sorting Operators in LINQ


Advertisements

A sorting operation allows ordering the elements of a sequence on basis of a single or more attributes.

Operator Description C# Query Expression Syntax VB Query Expression Syntax
OrderBy The operator sort values in an ascending order orderby Order By
OrderByDescending The operator sort values in a descending order orderby ... descending Order By ... Descending
ThenBy Executes a secondary sorting in an ascending order orderby …, … Order By …, …
ThenByDescending Executes a secondary sorting in a descending order orderby …, … descending Order By …, … Descending
Reverse Performs a reversal of the order of the elements in a collection Not Applicable Not Applicable

Example of OrderBy, OrderByDescending - Query Expression

C#

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

namespace Operators {
   class Program {
      static void Main(string[] args) {
      
         int[] num = { -20, 12, 6, 10, 0, -3, 1 };
			
         //create a query that obtain the values in sorted order
         var posNums = from n in num
                       orderby n
                       select n;
							  
         Console.Write("Values in ascending order: ");
     
         // Execute the query and display the results.
		 
         foreach (int i in posNums) 
            Console.Write(i + " \n");

            var posNumsDesc = from n in num
                              orderby n descending
                              select n;
										
            Console.Write("\nValues in descending order: ");

         // Execute the query and display the results.
		 
         foreach (int i in posNumsDesc) 
            Console.Write(i + " \n");

            Console.ReadLine();
      }
   }
}

VB

Module Module1

   Sub Main()
   
      Dim num As Integer() = {-20, 12, 6, 10, 0, -3, 1};

      Dim posNums = From n In num
                    Order By n
                    Select n;
						  
      Console.Write("Values in ascending order: ");

      For Each n In posNums
         Console.WriteLine(n)
      Next
 
      Dim posNumsDesc = From n In num
                       Order By n Descending
                       Select n;
							  
         Console.Write("Values in descending order: ");

      For Each n In posNumsDesc
         Console.WriteLine(n)
		
      Next
         Console.ReadLine()
		
   End Sub
  
End Module

When the above code in C# or VB is compiled and executed, it produces the following result −

Values in ascending order: -20 
-3 
0 
1 
6 
10 
12
Values in descending order: 12 
10 
6 
1 
0 
-3 
-20

In Thenby and ThenbyDescending operators, same syntax can be applied and sorting order will depend on more than one columns. Priority will be the column which is maintained first.

linq_query_operators.htm
Advertisements