Dictionary in C# (Programiz)

A Dictionary<TKey, TValue> in C# is a powerful collection that stores key-value pairs. It allows for efficient retrieval, insertion, and removal of elements based on their keys. This article provides a comprehensive overview of dictionaries in C#, offering practical examples and usage tips.

Features of Dictionary<TKey, TValue>

• Key-Value Pairs: Each key in the dictionary maps to a corresponding value.
• Unique Keys: All keys are unique, preventing duplicates.
• Efficient Access: Fast lookup and modification due to hash-based indexing.
• Generic: Can hold any data types as long as they implement the required interfaces.

Example: Creating and Using a Dictionary

Basic Operations

Here is how you can create a dictionary, add key-value pairs, retrieve values, and iterate through its items:

using System;
using System.Collections.Generic;

public class DictionaryProgram
{
    public static void Main()
    {
        // Create a dictionary with string keys and integer values
        Dictionary<string, int> fruits = new Dictionary<string, int>
        {
            { "Apple", 10 },
            { "Banana", 20 },
            { "Orange", 30 }
        };

        // Add a new key-value pair
        fruits["Pineapple"] = 40;

        // Access a value using the key
        int bananaCount = fruits["Banana"];
        Console.WriteLine($"Banana count: {bananaCount}");

        // Update an existing value
        fruits["Orange"] = 35;

        // Remove a key-value pair by key
        fruits.Remove("Apple");

        // Iterate through the dictionary using foreach
        Console.WriteLine("\nAll fruits in the dictionary:");
        foreach (KeyValuePair<string, int> fruit in fruits)
        {
            Console.WriteLine($"{fruit.Key}: {fruit.Value}");
        }
    }
}

Common Operations

1. Add(key, value): Adds a new key-value pair to the dictionary.
2. Remove(key): Deletes a key-value pair based on the key.
3. ContainsKey(key): Checks if a key exists in the dictionary.
4. TryGetValue(key, out value): Retrieves a value safely without throwing exceptions.
5. Count: Returns the number of key-value pairs.
6. Clear: Removes all pairs from the dictionary.

Best Practices

• Exception Handling: Handle exceptions gracefully when keys are not found.
• TryGetValue: Prefer TryGetValue for safe retrieval.
• Initial Capacity: Set an initial capacity if the size is known to minimize resizing.

Advanced Use Cases

• Configuration Settings: Store application configurations in key-value pairs.
• Data Indexing: Index different attributes for quick search and filtering.

Conclusion

A Dictionary<TKey, TValue> in C# is an essential collection for efficient key-value storage. Understanding its features, operations, and best practices will help you build effective data structures tailored to your application's requirements.