C# | Dictionary.Item[] Property

This property is used to get or set the value associated with the specified key in the Dictionary.

Syntax:

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

Here, key is the Key of the value to get or set.

Property Value: It is the value associated with the specified key. If the specified key is not found, a get operation throws a KeyNotFoundException, and a set operation creates a new element with the specified key.

Exceptions:



  • ArgumentNullException: If the key is null.
  • KeyNotFoundException: If the property is retrieved and key does not exist in the collection.

Example:

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// C# code to get or set the value
// associated with the specified key
using System;
using System.Collections;
using System.Collections.Generic;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a Dictionary named myDict
        Dictionary<string, string> myDict = new Dictionary<string, string>();
  
        // Adding key/value pairs in myDict
        myDict.Add("Australia", "Canberra");
        myDict.Add("Belgium", "Brussels");
        myDict.Add("Netherlands", "Amsterdam");
        myDict.Add("China", "Beijing");
        myDict.Add("Russia", "Moscow");
        myDict.Add("India", "New Delhi");
  
        // Displaying the key/value pairs in myDict
        foreach(KeyValuePair<string, string> k in myDict)
        {
            Console.WriteLine("Key = {0}, Value = {1}",
                              k.Key, k.Value);
        }
  
        // Displaying the value associated
        // with key "Russia"
        Console.Write("\nValue associated with Russia: ");
        Console.Write(myDict["Russia"]);
  
        // Setting the value associated with key "Russia"
        myDict["Russia"] = "Saint Petersburg";
  
        // Displaying the value associated
        // with key "Russia"
        Console.Write("\n\nValue associated with Russia After Setting: ");
        Console.Write(myDict["Russia"]);
  
        // Displaying the value associated
        // with key "India"
        Console.Write("\n\nValue associated with India: ");
        Console.Write(myDict["India"]);
  
        // Setting the value associated with key "India"
        myDict["India"] = "Mumbai";
  
        // Displaying the value associated
        // with key "India"
        Console.Write("\n\nValue associated with India After Setting: ");
        Console.Write(myDict["India"]);
        Console.WriteLine("\n");
  
        // Displaying the key/value pairs in myDict
        foreach(KeyValuePair<string, string> k1 in myDict)
        {
            Console.WriteLine("Key = {0}, Value = {1}",
                              k1.Key, k1.Value);
        }
    }
}

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Output:

Key = Australia, Value = Canberra
Key = Belgium, Value = Brussels
Key = Netherlands, Value = Amsterdam
Key = China, Value = Beijing
Key = Russia, Value = Moscow
Key = India, Value = New Delhi

Value associated with Russia: Moscow

Value associated with Russia After Setting: Saint Petersburg

Value associated with India: New Delhi

Value associated with India After Setting: Mumbai

Key = Australia, Value = Canberra
Key = Belgium, Value = Brussels
Key = Netherlands, Value = Amsterdam
Key = China, Value = Beijing
Key = Russia, Value = Saint Petersburg
Key = India, Value = Mumbai

Reference:



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