How to Read Dictionary in C#

In C#, the Dictionary<TKey, TValue> class provides a fast and efficient way to store key-value pairs. Reading data from a dictionary can be done in various ways depending on the structure of your program and the type of data you need. This article explains how to read a dictionary's keys and values in C# and provides practical examples.

Methods for Reading from a Dictionary

Accessing Values by Key

• Indexer (dictionary[key]): Retrieve the value directly using the key. An exception is thrown if the key does not exist.
• TryGetValue(key, out value): Retrieve the value safely without throwing exceptions.

Example: Using Indexer and TryGetValue

using System;
using System.Collections.Generic;

public class DictionaryReadExample
{
    public static void Main()
    {
        // Create a dictionary with some key-value pairs
        Dictionary<string, int> ages = new Dictionary<string, int>
        {
            { "Alice", 25 },
            { "Bob", 30 },
            { "Charlie", 35 }
        };

        // Using indexer to access values
        Console.WriteLine($"Alice's age: {ages["Alice"]}");
        Console.WriteLine($"Bob's age: {ages["Bob"]}");

        // Using TryGetValue to access values safely
        if (ages.TryGetValue("Charlie", out int charlieAge))
        {
            Console.WriteLine($"Charlie's age: {charlieAge}");
        }
        else
        {
            Console.WriteLine("Charlie not found.");
        }

        // Check for a non-existent key
        if (!ages.TryGetValue("Dave", out int daveAge))
        {
            Console.WriteLine("Dave not found.");
        }
    }
}

Iterating Through the Dictionary

• foreach Loop: Use a foreach loop to iterate through all key-value pairs.

Example: Iterating with a Foreach Loop

using System;
using System.Collections.Generic;

public class DictionaryIterationExample
{
    public static void Main()
    {
        // Create a dictionary with some key-value pairs
        Dictionary<string, string> capitals = new Dictionary<string, string>
        {
            { "USA", "Washington, D.C." },
            { "UK", "London" },
            { "France", "Paris" },
            { "Germany", "Berlin" }
        };

        // Iterate through the dictionary using a foreach loop
        Console.WriteLine("List of capitals:");
        foreach (KeyValuePair<string, string> kv in capitals)
        {
            Console.WriteLine($"{kv.Key}: {kv.Value}");
        }
    }
}

Using Keys and Values Collections

• Keys: Retrieve a collection of all the keys in the dictionary.
• Values: Retrieve a collection of all the values.

Example: Retrieving Keys and Values

using System;
using System.Collections.Generic;

public class DictionaryKeysValuesExample
{
    public static void Main()
    {
        // Create a dictionary with some key-value pairs
        Dictionary<string, int> products = new Dictionary<string, int>
        {
            { "Laptop", 1200 },
            { "Smartphone", 800 },
            { "Tablet", 600 }
        };

        // Display all keys
        Console.WriteLine("Product names:");
        foreach (string key in products.Keys)
        {
            Console.WriteLine(key);
        }

        // Display all values
        Console.WriteLine("\nProduct prices:");
        foreach (int value in products.Values)
        {
            Console.WriteLine(value);
        }
    }
}

Conclusion

In C#, reading data from a Dictionary<TKey, TValue> can be achieved using indexers, TryGetValue, and by iterating through the collection. Understanding these approaches helps ensure efficient and error-free data access in your applications.