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Home Forums How to sort the generic SortedList in descending order? – MindStick
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1 Answers

Ashutosh Patel
Ashutosh Patel 13 Jun 2024
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Sorting SortedList into Descending Order

The SortedList<TKey, TValue> class in C# does not have a built-in method to sort its elements directly in descending order. However, you can do this by creating a new list or collection and sorting the items from the original SortedList in order with it.

Example- 

Here a basic example to sort the SortedList into descending order in c#,

using System;
using System.Collections.Generic;
class Program
{
   static void Main()
   {
       // Creating a SortedList
       SortedList<int, string> sortedList = new SortedList<int, string>();
       // Add some items to the SortedList
       sortedList.Add(3, "Three");
       sortedList.Add(1, "One");
       sortedList.Add(2, "Two");
       // Sort the items in descending order
       List<KeyValuePair<int, string>> descendingList = new List<KeyValuePair<int, string>>(sortedList);
       descendingList.Sort((x, y) => y.Key.CompareTo(x.Key));
       // Print the sorted items
       Console.WriteLine("Descending Order");
       foreach (var item in descendingList)
       {
           Console.WriteLine("Key: {0}, Values: {1}", item.Key, item.Value);
       }
       // also sort the items in ascending order
       List<KeyValuePair<int, string>> ascendingList = new List<KeyValuePair<int, string>>(sortedList);
       ascendingList.Sort((x, y) => x.Key.CompareTo(y.Key));
       // Print the ascending order items
       Console.WriteLine("\nAscending Order");
       foreach (var item in ascendingList)
       {
           Console.WriteLine("Key: {0}, Values: {1}",item.Key, item.Value);
       }
       Console.ReadLine();
   }
}

In the above exaple-


We first create a sortedList called SortedList<int, string> and add some items to it.

We then create a List<KeyValuePair<int, string>> named descendingList for Descending order and ascendingList for Ascending order, and initialize it with the items from the original SortedList.

We use the Sort method of the List class to sort the items in descending order based on the key. We provide a custom comparison function using a lambda expression.

Finally, we print the orders.

Output-

Descending Order
Key: 3, Values: Three
Key: 2, Values: Two
Key: 1, Values: One

Ascending Order
Key: 1, Values: One
Key: 2, Values: Two
Key: 3, Values: Three

This will print the items from the original SortedList in descending order of their key.

Also, Read: How to write file using StreamWriter in C#?

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