Orderby clause in C#

The orderby clause in C# is used to sort elements in a collection based on one or more specified criteria. It supports both ascending (default) and descending order, and can be used with LINQ query expressions or method syntax.

Syntax

Following is the syntax for using orderby in query expression −

var result = from element in collection
             orderby element.Property [ascending|descending]
             select element;

Following is the syntax for method syntax using OrderBy() and OrderByDescending() −

var result = collection.OrderBy(x => x.Property);
var result = collection.OrderByDescending(x => x.Property);

Using orderby for Ascending Order

By default, orderby sorts elements in ascending order. The ascending keyword is optional −

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

class Demo {
   static void Main() {
      List<int> numbers = new List<int> { 45, 12, 78, 23, 56 };

      var ascendingOrder = from num in numbers
                          orderby num ascending
                          select num;

      Console.WriteLine("Ascending order:");
      foreach (int num in ascendingOrder) {
         Console.WriteLine(num);
      }
   }
}

The output of the above code is −

Ascending order:
12
23
45
56
78

Using orderby for Descending Order

Use the descending keyword to sort elements in reverse order −

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

class Demo {
   static void Main() {
      List<string> myList = new List<string>();
      myList.Add("iOS by Apple");
      myList.Add("Android by Google");
      myList.Add("Symbian by Nokia");

      var myLen = from element in myList
                  orderby element.Length descending
                  select element;
      Console.WriteLine("Descending order by length:");

      foreach (string str in myLen) {
         Console.WriteLine(str);
      }
   }
}

The output of the above code is −

Descending order by length:
Android by Google
Symbian by Nokia
iOS by Apple

Multiple Sorting Criteria

You can sort by multiple fields using comma-separated criteria −

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

class Student {
   public string Name { get; set; }
   public int Age { get; set; }
   public double Grade { get; set; }
}

class Demo {
   static void Main() {
      List<Student> students = new List<Student> {
         new Student { Name = "Alice", Age = 22, Grade = 85.5 },
         new Student { Name = "Bob", Age = 20, Grade = 92.0 },
         new Student { Name = "Charlie", Age = 22, Grade = 78.5 }
      };

      var sortedStudents = from student in students
                          orderby student.Age ascending, student.Grade descending
                          select student;

      Console.WriteLine("Sorted by Age (asc), then Grade (desc):");
      foreach (var student in sortedStudents) {
         Console.WriteLine($"{student.Name}: Age {student.Age}, Grade {student.Grade}");
      }
   }
}

The output of the above code is −

Sorted by Age (asc), then Grade (desc):
Bob: Age 20, Grade 92
Alice: Age 22, Grade 85.5
Charlie: Age 22, Grade 78.5

Comparison: Query vs Method Syntax

Conclusion

The orderby clause in C# provides a simple way to sort collections based on one or multiple criteria. It supports both ascending and descending orders, and can be combined with other LINQ operations to create powerful data queries for organizing and retrieving sorted data efficiently.