List<T>.Reverse Method is used to reverse the order of the elements in the List<T> or a portion of it. There are two methods in the overload list of List<T>.Reverse Method as follows:
CSharp
Output:
CSharp
Output:
CSharp
Output:
CSharp
- Reverse()
- Reverse(Int32, Int32)
Reverse() Method
This method is used to reverse the order of the elements in the entire List<T>. Syntax:public void Reverse ();Below programs illustrate the use of above discussed method: Example 1:
// C# Program to reverse the order of
// the elements in the entire List<T>
using System;
using System.Collections;
using System.Collections.Generic;
class Geeks {
// Main Method
public static void Main()
{
// Creating an List<T> of Integers
List<int> firstlist = new List<int>();
// Adding elements to List
for (int i = 1; i <= 5; i++) {
firstlist.Add(i);
}
Console.WriteLine("Elements Present in List:");
// Displaying the elements of List
foreach(int k in firstlist)
{
Console.WriteLine(k);
}
Console.WriteLine(" ");
Console.WriteLine("After Reversing: ");
// using method Reverse()
firstlist.Reverse();
// Displaying the elements of List
foreach(int k in firstlist)
{
Console.WriteLine(k);
}
}
}
Elements Present in List: 1 2 3 4 5 After Reversing: 5 4 3 2 1Example 2:
// C# Program to reverse the order of
// the elements in the entire List<T>
using System;
using System.Collections;
using System.Collections.Generic;
class Geeks {
// Main Method
public static void Main()
{
// Creating an List<T> of Integers
List<string> firstlist = new List<string>();
// Adding elements to List
firstlist.Add("Geeks");
firstlist.Add("C#");
firstlist.Add("Java");
firstlist.Add("C++");
Console.WriteLine("Elements Present in List:");
// Displaying the elements of List
foreach(string k in firstlist)
{
Console.WriteLine(k);
}
Console.WriteLine(" ");
Console.WriteLine("After Reversing: ");
// using method Reverse()
firstlist.Reverse();
// Displaying the elements of List
foreach(string k in firstlist)
{
Console.WriteLine(k);
}
}
}
Elements Present in List: Geeks C# Java C++ After Reversing: C++ Java C# Geeks
Reverse(Int32, Int32) Method
This method is used to reverse the order of the elements in the specified range. Syntax:public void Reverse (int index, int count);Parameters:
index: It is the zero-based starting index of the range which is to be reversed. count: It is the number of elements in the range which is to be reversed.Exceptions:
- ArgumentOutOfRangeException: If the index or count is less than zero.
- ArgumentException: If the index and count do not denote a valid range of elements in the List<T>.
// C# Program to reverse the order of
// sub range in the List<T>
using System;
using System.Collections;
using System.Collections.Generic;
class Geeks {
// Main Method
public static void Main()
{
// Creating an List<T> of Integers
List<string> firstlist = new List<string>();
// Adding elements to List
firstlist.Add("1st");
firstlist.Add("2nd");
firstlist.Add("3rd");
firstlist.Add("4th");
firstlist.Add("5th");
firstlist.Add("6th");
firstlist.Add("7th");
Console.WriteLine("Elements Present in List:");
// Displaying the elements of List
foreach(string k in firstlist)
{
Console.WriteLine(k);
}
Console.WriteLine(" ");
Console.WriteLine("After Reversing: ");
// Reversing the sub-range
// that starts from index 2
// i.e 3rd element, and
// count is 4 elements
firstlist.Reverse(2, 4);
// Displaying the elements of List
foreach(string k in firstlist)
{
Console.WriteLine(k);
}
}
}
Elements Present in List: 1st 2nd 3rd 4th 5th 6th 7th After Reversing: 1st 2nd 6th 5th 4th 3rd 7thExample 2:
// C# Program to reverse the order of
// sub range in the List<T>
using System;
using System.Collections;
using System.Collections.Generic;
class Geeks {
// Main Method
public static void Main()
{
// Creating an List<T> of Integers
List<string> firstlist = new List<string>();
// Adding elements to List
firstlist.Add("1st");
firstlist.Add("2nd");
firstlist.Add("3rd");
firstlist.Add("4th");
firstlist.Add("5th");
firstlist.Add("6th");
firstlist.Add("7th");
Console.WriteLine("Elements Present in List:");
// Displaying the elements of List
foreach(string k in firstlist)
{
Console.WriteLine(k);
}
Console.WriteLine(" ");
Console.WriteLine("After Reversing: ");
// taking negative index will give error
firstlist.Reverse(-1, 4);
// Displaying the elements of List
foreach(string k in firstlist)
{
Console.WriteLine(k);
}
}
}
RUntimeError:
Unhandled Exception: System.ArgumentOutOfRangeException: Non-negative number required. Parameter name: indexReference: