How to Swap Keys and Values in a Dictionary in C#

How to Swap Keys and Values in a Dictionary in C# ?

Answer

To swap keys and values in a dictionary in C#, you can use a `foreach` loop to iterate through the original dictionary and add each key-value pair to a new dictionary with the key and value swapped. This allows you to create a new dictionary where the keys and values are swapped.

✐ Examples

1 Swapping Keys and Values in a Dictionary Using a `foreach` Loop

We can swap keys and values in a dictionary in C# using a `foreach` loop. This example demonstrates how to declare and initialize a dictionary, use a `foreach` loop to swap the keys and values, and print the resulting dictionary.

For example,

We start by including the necessary namespace: using System.Collections.Generic;.
We declare and initialize a dictionary named originalDict with integer keys and string values.
We declare an empty dictionary named swappedDict to store the swapped key-value pairs.
We use a `foreach` loop to iterate through the original dictionary and add each key-value pair to the new dictionary with the key and value swapped.
We print the resulting dictionary.

C# Program

using System;
using System.Collections.Generic;

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

        // Declare an empty dictionary to store the swapped key-value pairs
        Dictionary<string, int> swappedDict = new Dictionary<string, int>();

        // Use a foreach loop to swap the keys and values
        foreach (var kvp in originalDict)
        {
            swappedDict[kvp.Value] = kvp.Key;
        }

        // Print the resulting dictionary
        Console.WriteLine("Swapped dictionary:");
        foreach (var kvp in swappedDict)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

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

2 Swapping Keys and Values in a Dictionary with Duplicate Values

We can swap keys and values in a dictionary with duplicate values in C# by checking for duplicates and handling them appropriately. This example demonstrates how to declare and initialize a dictionary with duplicate values, use a `foreach` loop to swap the keys and values while handling duplicates, and print the resulting dictionary.

For example,

We start by including the necessary namespace: using System.Collections.Generic;.
We declare and initialize a dictionary named originalDict with integer keys and string values, including duplicate values.
We declare an empty dictionary named swappedDict to store the swapped key-value pairs.
We use a `foreach` loop to iterate through the original dictionary, check for duplicate values, and add each key-value pair to the new dictionary with the key and value swapped.
We print the resulting dictionary.

C# Program

using System;
using System.Collections.Generic;

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

        // Declare an empty dictionary to store the swapped key-value pairs
        Dictionary<string, List<int>> swappedDict = new Dictionary<string, List<int>>();

        // Use a foreach loop to swap the keys and values
        foreach (var kvp in originalDict)
        {
            if (!swappedDict.ContainsKey(kvp.Value))
            {
                swappedDict[kvp.Value] = new List<int>();
            }
            swappedDict[kvp.Value].Add(kvp.Key);
        }

        // Print the resulting dictionary
        Console.WriteLine("Swapped dictionary:");
        foreach (var kvp in swappedDict)
        {
            Console.WriteLine("Key: {0}, Values: {1}", kvp.Key, string.Join(", ", kvp.Value));
        }
    }
}

Output

Swapped dictionary:
Key: One, Values: 1, 3
Key: Two, Values: 2

Summary

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

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