dictionary methods in c#

Dictionary Methods in C#

In C#, the Dictionary<TKey, TValue> class is a versatile collection that offers a variety of methods for efficiently managing key-value pairs. Understanding these methods will help you utilize dictionaries effectively for different programming tasks. This article provides an overview of key methods available in Dictionary<TKey, TValue> and how to use them with practical examples.

Common Methods of Dictionary<TKey, TValue>

Adding Elements

• Add(key, value): Adds a new key-value pair to the dictionary.

using System;
using System.Collections.Generic;

public class DictionaryAddExample
{
    public static void Main()
    {
        // Create a dictionary and add key-value pairs
        Dictionary<string, int> scores = new Dictionary<string, int>();
        scores.Add("Alice", 90);
        scores.Add("Bob", 85);
        scores.Add("Charlie", 95);

        // Print the scores
        Console.WriteLine("Initial scores:");
        foreach (KeyValuePair<string, int> kvp in scores)
        {
            Console.WriteLine($"{kvp.Key}: {kvp.Value}");
        }
    }
}

Retrieving Values

• Indexer (dictionary[key]): Retrieves the value associated with a key but throws an exception if the key is not found.
• TryGetValue(key, out value): Safely retrieves a value and returns true if successful; otherwise, returns false.

using System; using System.Collections.Generic; public class DictionaryRetrieveExample {    public static void Main()    {        // Create a dictionary with some initial data        Dictionary<string, int> ages = new Dictionary<string, int>        {            { "Alice", 28 },            { "Bob", 30 }        };        // Using indexer to retrieve a value        Console.WriteLine($"Bob's age: {ages["Bob"]}");        // Using TryGetValue to retrieve a value safely        if (ages.TryGetValue("Alice", out int aliceAge))        {            Console.WriteLine($"Alice's age: {aliceAge}");        }        else        {            Console.WriteLine("Alice not found.");        }        // Check for a non-existent key        if (!ages.TryGetValue("Charlie", out int charlieAge))        {            Console.WriteLine("Charlie not found.");        }    } }

Checking and Removing Elements

• ContainsKey(key): Checks if a key is present in the dictionary.
• Remove(key): Removes a key-value pair based on the key.

using System;
using System.Collections.Generic;

public class DictionaryRemoveExample
{
    public static void Main()
    {
        // Create a dictionary with initial data
        Dictionary<string, string> employees = new Dictionary<string, string>
        {
            { "E123", "John Doe" },
            { "E456", "Jane Smith" }
        };

        // Check if a specific employee ID exists
        string targetID = "E123";
        if (employees.ContainsKey(targetID))
        {
            Console.WriteLine($"Employee {targetID}: {employees[targetID]}");
        }

        // Remove an employee by ID
        employees.Remove("E123");

        // Confirm removal
        if (!employees.ContainsKey("E123"))
        {
            Console.WriteLine("Employee E123 has been removed.");
        }
    }
}

Other Useful Methods

• Count: Returns the number of key-value pairs.
• Clear: Removes all key-value pairs from the dictionary.
• Keys/Values: Returns collections of keys or values.

Conclusion

Dictionary<TKey, TValue> methods offer powerful ways to manage key-value pairs in C#. By understanding and using these methods effectively, you can implement efficient and reliable collections tailored to your application needs.