How to Sort a Dictionary by Keys in C# - Step by Step Examples

How to Sort a Dictionary by Keys in C# ?

Answer

To sort a dictionary by keys in C#, you can use the `OrderBy` method from the `System.Linq` namespace and convert the sorted result back to a dictionary using the `ToDictionary` method. This allows you to create a new dictionary with the key-value pairs sorted by key.

✐ Examples

1 Sorting a Dictionary by Keys Using `OrderBy`

We can sort a dictionary by keys in C# using the `OrderBy` method from the `System.Linq` namespace. This example demonstrates how to declare and initialize a dictionary, use the `OrderBy` method to sort the dictionary by keys, and print the sorted dictionary.

For example,

We start by including the necessary namespaces: using System.Collections.Generic; and using System.Linq;.
We declare and initialize a dictionary named myDictionary with integer keys and string values.
We use the `OrderBy` method to sort the dictionary by keys.
We convert the sorted result to a dictionary using the `ToDictionary` method.
We print the sorted dictionary.

C# Program

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        // Declare and initialize a dictionary
        Dictionary<int, string> myDictionary = new Dictionary<int, string>
        {
            {3, "Three"},
            {1, "One"},
            {2, "Two"}
        };

        // Sort the dictionary by keys using OrderBy
        Dictionary<int, string> sortedDict = myDictionary
            .OrderBy(kvp => kvp.Key)
            .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

        // Print the sorted dictionary
        Console.WriteLine("Sorted dictionary:");
        foreach (var kvp in sortedDict)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

Sorted dictionary:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three

2 Sorting a Dictionary by Keys in Descending Order

We can sort a dictionary by keys in descending order in C# using the `OrderByDescending` method from the `System.Linq` namespace. This example demonstrates how to declare and initialize a dictionary, use the `OrderByDescending` method to sort the dictionary by keys in descending order, and print the sorted dictionary.

For example,

We start by including the necessary namespaces: using System.Collections.Generic; and using System.Linq;.
We declare and initialize a dictionary named myDictionary with integer keys and string values.
We use the `OrderByDescending` method to sort the dictionary by keys in descending order.
We convert the sorted result to a dictionary using the `ToDictionary` method.
We print the sorted dictionary.

C# Program

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        // Declare and initialize a dictionary
        Dictionary<int, string> myDictionary = new Dictionary<int, string>
        {
            {3, "Three"},
            {1, "One"},
            {2, "Two"}
        };

        // Sort the dictionary by keys in descending order using OrderByDescending
        Dictionary<int, string> sortedDict = myDictionary
            .OrderByDescending(kvp => kvp.Key)
            .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

        // Print the sorted dictionary
        Console.WriteLine("Sorted dictionary:");
        foreach (var kvp in sortedDict)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

Sorted dictionary:
Key: 3, Value: Three
Key: 2, Value: Two
Key: 1, Value: One

Summary

In this tutorial, we learned How to Sort a Dictionary by Keys in C# language with well detailed examples.

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