How to sort a list in C# | List.Sort() Method Set -2
Last Updated :
22 Sep, 2021
List<T>.Sort() Method is used to sort the elements or a portion of the elements in the List<T> using either the specified or default IComparer<T> implementation or a provided Comparison<T> delegate to compare list elements. There are total 4 methods in the overload list of this method as follows:
- Sort(IComparer<T>)
- Sort(Int32, Int32, IComparer)
- Sort()
- Sort(Comparison<T>)
Here, the first two methods are discussed in
Set - 1. So, We will discuss the last two methods.
Sort() Method
This method is used to sort the elements in the entire List<T> using the default comparer.
Syntax: public void Sort ();
Exception: This method will give InvalidOperationException if the default Comparer cannot find an implementation of the IComparable<T> generic interface or the IComparable interface for type T.
Example 1:
csharp
// C# program to demonstrate the
// use of List<T>.Sort() method
using System;
using System.Collections.Generic;
class GFG {
// Main Method
public static void Main()
{
// List initialize
List<int> list1 = new List<int> {
// list elements
1, 5, 6, 2, 4, 3
};
Console.WriteLine("Original List");
foreach(int g in list1)
{
// Display Original List
Console.WriteLine(g);
}
Console.WriteLine("\nSorted List");
// use of List<T>.Sort() method
list1.Sort();
foreach(int g in list1)
{
// Display sorted list
Console.WriteLine(g);
}
}
}
Output:
Original List
1
5
6
2
4
3
Sorted List
1
2
3
4
5
6
Example 2:
csharp
// C# program to demonstrate the
// use of List<T>.Sort() method
using System;
using System.Collections.Generic;
class GFG {
// Main Method
public static void Main()
{
List<string> list1 = new List<string>();
// list elements
list1.Add("A");
list1.Add("I");
list1.Add("G");
list1.Add("B");
list1.Add("E");
list1.Add("H");
list1.Add("F");
list1.Add("C");
list1.Add("D");
Console.WriteLine("Original List");
// Display Original List
Display(list1);
Console.WriteLine("\nSorted List");
// use of List.Sort() method
list1.Sort();
// Display sorted List
Display(list1);
}
// Display function
public static void Display(List<string> list)
{
foreach(string g in list)
{
Console.Write(g + " ");
}
}
}
Output:
Original List
A I G B E H F C D
Sorted List
A B C D E F G H I
Example 3:
csharp
// C# program to demonstrate the
// use of List<T>.Sort() method
using System;
using System.Collections.Generic;
public class GFG {
// Main Method
public static void Main()
{
// array elements
String[] list = {"C++", "Java", "C",
"Python", "HTML", "CSS",
"Scala", "Ruby", "Perl"};
var list1 = new List<String>();
// "AddRange" method to add the
// string array elements into the List
list1.AddRange(list);
Console.WriteLine("List in unsorted order: ");
Display(list1);
Console.WriteLine(Environment.NewLine);
// using List.Sort() method
list1.Sort();
Console.WriteLine("List in sorted order: ");
Display(list1);
}
// Display method
static void Display(List<string> list)
{
foreach(string g in list)
{
Console.Write(g + "\t");
}
}
}
Output:
List in unsorted order:
C++ Java C Python HTML CSS Scala Ruby Perl
List in sorted order:
C C++ CSS HTML Java Perl Python Ruby Scala
Sort(IComparer<T>) Method
This method is used to sort the elements in the entire List<T> using the specified comparer.
Syntax: public void Sort (Comparison<T> comparison);
Parameter:
comparison: It is the IComparer<T> implementation to use when comparing elements, or null to use the default comparer Default.
Exceptions:
- ArgumentNullException: If the comparer is null, and the default comparer Default cannot find implementation of the IComparable<T> generic interface or the IComparable interface for type T.
- ArgumentException: If the implementation of comparer caused an error during the sort. For example, comparer might not return 0 when comparing an item with itself.
Below programs illustrate the use of the above-discussed method:
Example 1:
csharp
// C# program to demonstrate the use of
// List<T>.Sort(comparison <T>) method
using System;
using System.Collections.Generic;
class GFG {
private static int Geek(string x,
string y)
{
if (x == null) {
if (y == null) {
// If x and y is null
// then they are equal
return 0;
}
else {
// If x is null but y is not
// null then y is greater.
return -1;
}
}
else {
if (y == null) {
return 1;
}
else {
// If the strings are of equal length,
// sort them with string comparison.
return x.CompareTo(y);
}
}
}
// Main Method
public static void Main()
{
List<string> list1 = new List<string>();
// list elements
list1.Add("AB");
list1.Add("CD");
list1.Add("GH");
list1.Add("EF");
list1.Add("IJ");
list1.Add("KL");
Console.WriteLine("Original List :");
// displaying original list
Display(list1);
Console.WriteLine("\nSort with generic Comparison object :");
// Sort(Comparison<t>) method
//"Geek" is Comparison object
list1.Sort(Geek);
// displaying sorted list
Display(list1);
}
// display function
private static void Display(List<string> list)
{
foreach(string g in list)
{
Console.WriteLine(g);
}
}
}
Output:
Original List :
AB
CD
GH
EF
IJ
KL
Sort with generic Comparison object :
AB
CD
EF
GH
IJ
KL
Example 2:
csharp
// C# program to demonstrate the use of
// List<T>.Sort(comparison <T>) method
using System;
using System.Collections.Generic;
class GFG {
private static int Geek(int x, int y)
{
if (x == 0) {
if (y == 0) {
// If x and y is null
// then they are equal
return 0;
}
else {
// If x is null but y is not
// null then y is greater.
return -1;
}
}
else {
if (y == 0) {
return 1;
}
else {
// If the strings are of equal length,
// sort them with string comparison.
return x.CompareTo(y);
}
}
}
public static void Main()
{
List<int> list1 = new List<int>();
// list elements
list1.Add(2);
list1.Add(5);
list1.Add(6);
list1.Add(4);
list1.Add(1);
list1.Add(3);
Console.WriteLine("Original List :");
// displaying original list
Display(list1);
Console.WriteLine("\nSort with generic "+
"Comparison object :");
// Sort(Comparison<t>) method
//"Geek" is Comparison object
list1.Sort(Geek);
// displaying sorted list
Display(list1);
}
// display function
private static void Display(List<int> list)
{
foreach(int g in list)
{
Console.WriteLine(g);
}
}
}
Output:
Original List :
2
5
6
4
1
3
Sort with generic Comparison object :
1
2
3
4
5
6
Reference:
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