Difference Between Hashtable And Dictionary In C#

In this post, we will explore the variances between Hashtable and Dictionary in C#. Prior to delving into their distinctions, it is essential to understand Hashtable and Dictionary in C# along with examples.

Introduction of Hashtable:

A data structure known as Hashtable in C# is designed to store key/value pairs. It can be found within the System namespace for collections.

Overview of how it works:

• ✅ Key/Value Pair: Every entry in a hashtable consists of a separate key and its matching information. Values in the hashtable can be replicated, but identifiers need to be distinct.
• ✅ Hashing: Hashtable maps keys to their associated values internally using a hashing technique. As a consequence, values may be efficiently retrieved using their identification numbers.
• ✅ Quick Lookup: Hashtables offer quick lookup times for values based on their keys due to hashing. The average length of time required to get an element from a hashtable generally remains constant.
• ✅ Dynamic Sizing: A hashtable constantly changes size to make room for extra items. This helps preserve efficient performance even when the Hashtable's element count fluctuates.
• ✅ No Order Guarantee: The order of all the components in a hashtable is not guaranteed, in contrast to several other collection types in C#, such as list and dictionaries. The sequence in which elements are kept in the hashtable is not fixed.

Example:

Let's consider a scenario to demonstrate the implementation of a hashtable in C#:

using System;
using System.Collections;
class Program
{
    static void Main()
    {
        // Creating a new Hashtable instance
        Hashtable hashtable = new Hashtable();

        // Adding key/value pairs to the Hashtable
        hashtable.Add("apple", 10);
        hashtable.Add("banana", 20);
        hashtable.Add("orange", 30);

        // Accessing values using keys
        Console.WriteLine("Value of 'apple': " + hashtable["apple"]);
        Console.WriteLine("Value of 'banana': " + hashtable["banana"]);

        // Modifying the value associated with a key
        hashtable["orange"] = 40;

        // Removing a key/value pair
        hashtable.Remove("banana");

        // Iterating over the Hashtable
        foreach (DictionaryEntry entry in hashtable)
        {
            Console.WriteLine("Key: " + entry.Key + ", Value: " + entry.Value);
        }
    }
}

Output:

Value of 'apple': 10
Value of 'banana': 20
Key: apple, Value: 10
Key: orange, Value: 40

Explanation:

In this instance, the provided C# code demonstrates the utilization of the Hashtable collection class from the System namespace for managing collections. Within the Main function, a fresh Hashtable instance named "hashtable" is instantiated. Subsequently, the Add method is employed to insert key/value pairs into this hashtable. Since each key corresponds to a value, it allows for the efficient retrieval of values based on their corresponding keys.

The following code snippet demonstrates how to retrieve values from a hashtable by referencing their respective keys once key-value pairs have been added. By using square brackets along with the specific key name, the associated values can be accessed directly.

Following that, the code updates the value associated with the key "orange" by assigning it a fresh value. Furthermore, the item linked to the key "banana" is removed from the hashtable using the delete function to eliminate a key/value pair.

Finally, the code employs a foreach loop to iterate through the remaining key/value pairs in the hashtable. Each DictionaryEntry object signifies an entry in the hashtable containing both the key and the value. The modified contents of the hashtable are then exhibited on the console by showcasing the key and value of each individual item.

Introduction Dictionary in C#:

A Dictionary is a generic collection class in C# that facilitates quick lookup, insertion, and deletion decisions by storing key/value pairs. It's included in the System.Collections namespace. Here is a summary of its salient characteristics:

• ✅ Key/Value Pair: Every element within a dictionary has a distinct key and a corresponding value, just like in a hashtable. Variables can be replicated, but keys in the Dictionary must be distinct.
• ✅ Firmly Typed: In contrast to Hashtable, the dictionary is firmly typed, which holds objects and necessitates boxing and unpacking. It implies that type correctness is provided and boxing/unboxing operations cannot be performed because we provide the types for each of the keys and values at the time we declare a Dictionary instance.
• ✅ Type Safety and Performance: Dictionary operates better than Hashtable due to its strong typing, particularly when handling different types of values and eliminating pointless type conversions.
• ✅ Quick Lookup: Dictionary employs hashing internally, such as Hashtable, which provides quick lookup speeds for values depending on their keys. The average time complexity for retrieving an element from a dictionary is usually constant.
• ✅ No Order Guarantee: Dictionary, like Hashtable, provides no promises about the arrangement of its components.
• ✅ Dictionary support for Language Integrated Query (LINQ): LINQ enables us to work with the key/value pairs that are stored in the Dictionary by doing projections, queries, and transformations.

Example:

Let's consider an example to demonstrate the usage of a dictionary in C#:

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Creating a new Dictionary instance with string keys and int values
        Dictionary<string, int> dictionary = new Dictionary<string, int>();

        // Adding key/value pairs to the Dictionary
        dictionary.Add("apple", 10);
        dictionary.Add("banana", 20);
        dictionary.Add("orange", 30);

        // Accessing values using keys
        Console.WriteLine("Value of 'apple': " + dictionary["apple"]);
        Console.WriteLine("Value of 'banana': " + dictionary["banana"]);

        // Modifying the value associated with a key
        dictionary["orange"] = 40;

        // Removing a key/value pair
        dictionary.Remove("banana");

        // Iterating over the Dictionary
        foreach (KeyValuePair<string, int> kvp in dictionary)
        {
            Console.WriteLine("Key: " + kvp.Key + ", Value: " + kvp.Value);
        }
    }
}

Output:

Value of 'apple': 10
Value of 'banana': 20
Key: apple, Value: 10
Key: orange, Value: 40

Explanation:

The representation of the dictionary is illustrated in the provided C# script, showcasing the utilization of a collection type designed for holding key/value pairs. Within the code, a new instance of a Dictionary object named "dictionary" is instantiated, housing a mix of integer and string keys alongside values. Following this, the dictionary is populated with pairs representing the quantity of various fruits.

The script exemplifies the process of modifying a value associated with a specific key and retrieving values based on their respective keys. Additionally, it demonstrates the removal of a key/value pair from the dictionary. Towards the end, the code outputs each key/value pair onto the console while iterating through the word list. This example effectively showcases fundamental tasks in C# such as insertion, retrieval, modification, and deletion of items within a dictionary.

Main differences between Hashtable and Dictionary in C#

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There are several key distinctions between Hashtable and Dictionary in C#. Some primary variations between hashtable and dictionary are outlined below: