How to add key/value pairs in SortedList in C#?

A SortedList in C# is a collection that stores key/value pairs sorted by keys. The Add() method is the primary way to insert key/value pairs into a SortedList, automatically maintaining sorted order based on the keys.

Syntax

Following is the syntax for adding key/value pairs to a SortedList −

SortedList sortedList = new SortedList();
sortedList.Add(key, value);

Parameters

• key − The key of the element to add. Cannot be null and must be unique.

• value − The value of the element to add. Can be null.

Using Add() Method

Example

using System;
using System.Collections;

public class Demo {
   public static void Main(String[] args) {
      SortedList list = new SortedList();
      list.Add("A", "Jacob");
      list.Add("B", "Sam");
      list.Add("C", "Tom");
      list.Add("D", "John");
      list.Add("E", "Tim");
      list.Add("F", "Mark");
      list.Add("G", "Gary");
      list.Add("H", "Nathan");
      list.Add("I", "Shaun");
      list.Add("J", "David");
      
      ICollection col1 = list.Values;
      Console.WriteLine("Values...");
      foreach(string s in col1)
         Console.WriteLine(s);
      
      ICollection col2 = list.Keys;
      Console.WriteLine("\nKeys...");
      foreach(string s in col2)
         Console.WriteLine(s);
   }
}

The output of the above code is −

Values...
Jacob
Sam
Tom
John
Tim
Mark
Gary
Nathan
Shaun
David

Keys...
A
B
C
D
E
F
G
H
I
J

Working with SortedList Operations

Example

using System;
using System.Collections;

public class Demo {
   public static void Main(String[] args) {
      SortedList sortedList = new SortedList();
      sortedList.Add("A", "1");
      sortedList.Add("B", "2");
      sortedList.Add("C", "3");
      sortedList.Add("D", "4");
      sortedList.Add("E", "5");
      sortedList.Add("F", "6");
      sortedList.Add("G", "7");
      sortedList.Add("H", "8");
      sortedList.Add("I", "9");
      sortedList.Add("J", "10");
      
      Console.WriteLine("SortedList elements...");
      foreach(DictionaryEntry d in sortedList) {
         Console.WriteLine("Key = " + d.Key + ", Value = " + d.Value);
      }
      Console.WriteLine("Count of SortedList key-value pairs = " + sortedList.Count);
      
      sortedList.RemoveAt(3);
      Console.WriteLine("\nEnumerator to iterate through the SortedList...");
      IDictionaryEnumerator demoEnum = sortedList.GetEnumerator();
      while (demoEnum.MoveNext())
         Console.WriteLine("Key = " + demoEnum.Key + ", Value = " + demoEnum.Value);
      Console.WriteLine("Count of SortedList key-value pairs (Updated) = " + sortedList.Count);
   }
}

The output of the above code is −

SortedList elements...
Key = A, Value = 1
Key = B, Value = 2
Key = C, Value = 3
Key = D, Value = 4
Key = E, Value = 5
Key = F, Value = 6
Key = G, Value = 7
Key = H, Value = 8
Key = I, Value = 9
Key = J, Value = 10
Count of SortedList key-value pairs = 10

Enumerator to iterate through the SortedList...
Key = A, Value = 1
Key = B, Value = 2
Key = C, Value = 3
Key = E, Value = 5
Key = F, Value = 6
Key = G, Value = 7
Key = H, Value = 8
Key = I, Value = 9
Key = J, Value = 10
Count of SortedList key-value pairs (Updated) = 9

Key Features

• Automatic Sorting − Elements are automatically sorted by keys when added.

• Unique Keys − Each key must be unique; duplicate keys will throw an exception.

• Index Access − Elements can be accessed by index or key.

• Performance − O(log n) time complexity for Add, Remove, and search operations.

Conclusion

The Add() method is the primary way to insert key/value pairs into a SortedList in C#. The SortedList automatically maintains sorted order based on keys and provides efficient access to both keys and values through various collection interfaces.