CaseInsensitiveHashCodeProvider Class

Overview

Provides a case-insensitive hash code implementation.

The CaseInsensitiveHashCodeProvider class implements the IHashCodeProvider interface, providing a hash code based on the string's case-insensitive representation. This is particularly useful when storing strings in hash tables (like `Hashtable`) where case sensitivity needs to be ignored for key comparisons. It ensures that strings differing only in case will produce the same hash code, facilitating case-insensitive lookups.

Syntax

public sealed class CaseInsensitiveHashCodeProvider : IHashCodeProvider
            

Introduction

In .NET, hashing is a fundamental mechanism for efficient data retrieval in collection types such as dictionaries and hash tables. By default, string comparisons and hash code generation in .NET are case-sensitive. The CaseInsensitiveHashCodeProvider addresses scenarios where case sensitivity is undesirable. It provides a way to generate a hash code for a string that is independent of its casing, making it compatible with collections that require case-insensitive key matching.

Constructors

Properties

This class does not contain any public properties.

Methods

Remarks

The CaseInsensitiveHashCodeProvider is typically used in conjunction with a case-insensitive comparer when initializing a Hashtable. For example, you would pass an instance of CaseInsensitiveHashCodeProvider as the hashProvider argument to the Hashtable constructor along with an instance of CaseInsensitiveComparer for the IComparer argument.

While CaseInsensitiveHashCodeProvider was a common pattern, modern .NET development often favors generic collections like Dictionary<TKey, TValue>, which can be initialized with a specific IEqualityComparer<TKey>, offering more flexibility and type safety.

Requirements

Code Example

The following example demonstrates how to use CaseInsensitiveHashCodeProvider and CaseInsensitiveComparer with a Hashtable to store and retrieve elements in a case-insensitive manner.

using System;
using System.Collections;

public class Example
{
    public static void Main()
    {
        // Create a case-insensitive comparer and hash code provider
        IComparer caseInsensitiveComparer = CaseInsensitiveComparer.Default;
        IHashCodeProvider hashCodeProvider = new CaseInsensitiveHashCodeProvider();

        // Initialize a Hashtable with case-insensitive behavior
        Hashtable myTable = new Hashtable(hashCodeProvider, caseInsensitiveComparer);

        // Add elements with different casing
        myTable.Add("apple", 1);
        myTable.Add("Banana", 2);
        myTable.Add("CHERRY", 3);

        // Retrieve elements, demonstrating case insensitivity
        Console.WriteLine("Value for 'Apple': " + myTable["Apple"]);      // Output: Value for 'Apple': 1
        Console.WriteLine("Value for 'banana': " + myTable["banana"]);    // Output: Value for 'banana': 2
        Console.WriteLine("Value for 'Cherry': " + myTable["Cherry"]);    // Output: Value for 'Cherry': 3

        // Check if a key exists, demonstrating case insensitivity
        Console.WriteLine("Contains key 'APPLE': " + myTable.ContainsKey("APPLE")); // Output: Contains key 'APPLE': True
        Console.WriteLine("Contains key 'Date': " + myTable.ContainsKey("Date"));   // Output: Contains key 'Date': False
    }
}