SortedDictionary.Item[] Property in C#

The SortedDictionary.Item[] property in C# provides indexer access to get or set values associated with specified keys in a sorted dictionary. This property allows you to access dictionary elements using square bracket notation, making it convenient to retrieve and modify values.

Syntax

Following is the syntax for the SortedDictionary.Item[] property −

public TValue this[TKey key] { get; set; }

Parameters

• key − The key of the value to get or set of type TKey.

Return Value

Returns the value of type TValue associated with the specified key. If the key is not found during a get operation, a KeyNotFoundException is thrown.

Using Item[] Property for Getting Values

Example

using System;
using System.Collections.Generic;

public class Demo {
    public static void Main() {
        SortedDictionary<int, string> sortedDict = new SortedDictionary<int, string>();
        sortedDict.Add(1, "One");
        sortedDict.Add(2, "Two");
        sortedDict.Add(3, "Three");
        sortedDict.Add(4, "Four");
        sortedDict.Add(5, "Five");
        sortedDict.Add(6, "Six");
        
        Console.WriteLine("SortedDictionary key-value pairs...");
        foreach (var pair in sortedDict) {
            Console.WriteLine("Key = " + pair.Key + ", Value = " + pair.Value);
        }
        
        Console.WriteLine("Count of SortedDictionary key-value pairs = " + sortedDict.Count);
        Console.WriteLine("Value at key 5 = " + sortedDict[5]);
        Console.WriteLine("Value at key 2 = " + sortedDict[2]);
    }
}

The output of the above code is −

SortedDictionary key-value pairs...
Key = 1, Value = One
Key = 2, Value = Two
Key = 3, Value = Three
Key = 4, Value = Four
Key = 5, Value = Five
Key = 6, Value = Six
Count of SortedDictionary key-value pairs = 6
Value at key 5 = Five
Value at key 2 = Two

Using Item[] Property for Setting Values

Example

using System;
using System.Collections.Generic;

public class Demo {
    public static void Main() {
        SortedDictionary<int, string> sortedDict = new SortedDictionary<int, string>();
        sortedDict.Add(1, "SUV");
        sortedDict.Add(2, "MUV");
        sortedDict.Add(3, "Utility Vehicle");
        sortedDict.Add(4, "AUV");
        sortedDict.Add(5, "Hatchback");
        
        Console.WriteLine("Original value at key 5: " + sortedDict[5]);
        
        // Update existing value
        sortedDict[5] = "Crossover";
        Console.WriteLine("Updated value at key 5: " + sortedDict[5]);
        
        // Add new key-value pair using indexer
        sortedDict[6] = "Convertible";
        Console.WriteLine("New value at key 6: " + sortedDict[6]);
        
        Console.WriteLine("\nAll key-value pairs:");
        foreach (var pair in sortedDict) {
            Console.WriteLine("Key = " + pair.Key + ", Value = " + pair.Value);
        }
    }
}

The output of the above code is −

Original value at key 5: Hatchback
Updated value at key 5: Crossover
New value at key 6: Convertible

All key-value pairs:
Key = 1, Value = SUV
Key = 2, Value = MUV
Key = 3, Value = Utility Vehicle
Key = 4, Value = AUV
Key = 5, Value = Crossover
Key = 6, Value = Convertible

Key Behavior

• When using the getter (sortedDict[key]), if the key doesn't exist, a KeyNotFoundException is thrown.

• When using the setter (sortedDict[key] = value), if the key exists, its value is updated. If the key doesn't exist, a new key-value pair is added.

• Keys in SortedDictionary are automatically maintained in sorted order.

Conclusion

The SortedDictionary.Item[] property provides convenient indexer access for getting and setting values by key. It automatically handles both value updates for existing keys and insertion of new key-value pairs, while maintaining the sorted order of keys in the dictionary.