Reverse the order of the elements in the entire List or in the specified range in C#

The List<T>.Reverse() method in C# allows you to reverse the order of elements in a List. You can reverse the entire list or reverse a specific range of elements within the list.

Syntax

Following is the syntax for reversing the entire list −

list.Reverse();

Following is the syntax for reversing a specified range of elements −

list.Reverse(int index, int count);

Parameters

• index − The zero-based starting index of the range to reverse.

• count − The number of elements in the range to reverse.

Using Reverse() for Entire List

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(String[] args) {
      List<int> list = new List<int>();
      list.Add(5);
      list.Add(10);
      list.Add(20);
      list.Add(50);
      list.Add(100);
      
      Console.WriteLine("Original List:");
      foreach (int i in list) {
         Console.WriteLine(i);
      }
      
      list.Reverse();
      Console.WriteLine("\nReversed List:");
      foreach (int i in list) {
         Console.WriteLine(i);
      }
   }
}

The output of the above code is −

Original List:
5
10
20
50
100

Reversed List:
100
50
20
10
5

Using Reverse() for Specified Range

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(String[] args) {
      List<String> list = new List<String>();
      list.Add("One");
      list.Add("Two");
      list.Add("Three");
      list.Add("Four");
      list.Add("Five");
      list.Add("Six");
      list.Add("Seven");
      list.Add("Eight");
      
      Console.WriteLine("Original List:");
      foreach (string res in list) {
         Console.WriteLine(res);
      }
      
      list.Reverse(2, 4);
      Console.WriteLine("\nReversed 4 elements starting from index 2:");
      foreach (string res in list) {
         Console.WriteLine(res);
      }
   }
}

The output of the above code is −

Original List:
One
Two
Three
Four
Five
Six
Seven
Eight

Reversed 4 elements starting from index 2:
One
Two
Six
Five
Four
Three
Seven
Eight

Common Use Cases

• Sorting in descending order − First sort the list, then reverse it.

• Undo operations − Reverse a portion of the list to restore previous state.

• Algorithm implementations − Many algorithms require reversing portions of arrays or lists.

• Data display − Show most recent items first by reversing chronologically ordered data.

Conclusion

The List<T>.Reverse() method provides an efficient way to reverse elements in a List. Use Reverse() to reverse the entire list or Reverse(index, count) to reverse only a specific range of elements, making it useful for various data manipulation scenarios.