Hashtable in c# with example

Hashtable in C# with Example

In C#, the Hashtable class is a collection that stores key-value pairs. It allows efficient access and management of data using keys. Although it's been largely replaced by the generic Dictionary<TKey, TValue>, Hashtable is still relevant in certain scenarios. This article provides an overview of Hashtable and a practical example of its usage.

Features of Hashtable

• Key-Value Pair Storage: Stores objects as key-value pairs.
• Non-Generic: Keys and values are stored as objects.
• Null Handling: Supports null values and keys.
• Thread Safety: Limited support for thread safety through the SyncRoot property.
• Boxing/Unboxing: Requires boxing/unboxing for value types.

Example: Creating and Using a Hashtable

Basic Operations

Here's how to create a Hashtable, add key-value pairs, and read data:

using System;
using System.Collections;

public class HashtableExample
{
    public static void Main()
    {
        // Create a new Hashtable
        Hashtable table = new Hashtable
        {
            { "USA", "Washington, D.C." },
            { "UK", "London" },
            { "France", "Paris" },
            { "Germany", "Berlin" }
        };

        // Add a new key-value pair
        table["Japan"] = "Tokyo";

        // Access values using keys
        Console.WriteLine($"Capital of USA: {table["USA"]}");
        Console.WriteLine($"Capital of Japan: {table["Japan"]}");

        // Check if a key exists
        string country = "Italy";
        if (!table.ContainsKey(country))
        {
            Console.WriteLine($"Key '{country}' not found.");
        }

        // Remove a key-value pair
        table.Remove("France");

        // Iterate through the hashtable using a foreach loop
        Console.WriteLine("\nRemaining elements in the hashtable:");
        foreach (DictionaryEntry entry in table)
        {
            Console.WriteLine($"{entry.Key}: {entry.Value}");
        }
    }
}

Key Operations

1. Add: Adds a new key-value pair using Add(key, value).
2. Remove: Removes a key-value pair using Remove(key).
3. ContainsKey: Checks if a specific key exists.
4. Count: Returns the number of key-value pairs.
5. Clear: Removes all key-value pairs from the hashtable.

Best Practices

• Avoid Null Keys: Although Hashtable allows null keys, it's better to use non-null keys for consistent data management.
• Type Safety: Handle value types carefully to avoid errors due to boxing/unboxing.
• Thread Safety: Use SyncRoot or a synchronized wrapper for multi-threaded scenarios.

Conclusion

Hashtable in C# is a versatile collection for managing key-value pairs, especially when you require non-generic data handling or compatibility with legacy code. By understanding its features, operations, and best practices, you can leverage it effectively in your applications