How to Filter a Dictionary Based on Keys in C# - Step by Step Examples

How to Filter a Dictionary Based on Keys in C# ?

Answer

To filter a dictionary based on keys in C#, you can use the `Where` method from the `System.Linq` namespace and convert the filtered result back to a dictionary using the `ToDictionary` method. This allows you to create a new dictionary with the key-value pairs that satisfy a specific condition based on keys.

✐ Examples

1 Filtering a Dictionary Based on Keys Using `Where`

We can filter a dictionary based on keys in C# using the `Where` method from the `System.Linq` namespace. This example demonstrates how to declare and initialize a dictionary, use the `Where` method to filter the dictionary based on keys, and print the filtered 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 `Where` method to filter the dictionary to include only keys that are greater than 1.
We convert the filtered result to a dictionary using the `ToDictionary` method.
We print the filtered 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>
        {
            {1, "One"},
            {2, "Two"},
            {3, "Three"}
        };

        // Filter the dictionary to include only keys greater than 1
        Dictionary<int, string> filteredDict = myDictionary
            .Where(kvp => kvp.Key > 1)
            .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

        // Print the filtered dictionary
        Console.WriteLine("Filtered dictionary:");
        foreach (var kvp in filteredDict)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

Filtered dictionary:
Key: 2, Value: Two
Key: 3, Value: Three

2 Filtering a Dictionary to Include Only Specific Keys

We can filter a dictionary to include only specific keys in C# using the `Where` method from the `System.Linq` namespace. This example demonstrates how to declare and initialize a dictionary, use the `Where` method to filter the dictionary to include only the keys 1 and 3, and print the filtered 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 `Where` method to filter the dictionary to include only the keys 1 and 3.
We convert the filtered result to a dictionary using the `ToDictionary` method.
We print the filtered 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>
        {
            {1, "One"},
            {2, "Two"},
            {3, "Three"}
        };

        // Filter the dictionary to include only the keys 1 and 3
        Dictionary<int, string> filteredDict = myDictionary
            .Where(kvp => kvp.Key == 1 || kvp.Key == 3)
            .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

        // Print the filtered dictionary
        Console.WriteLine("Filtered dictionary:");
        foreach (var kvp in filteredDict)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

Filtered dictionary:
Key: 1, Value: One
Key: 3, Value: Three

Summary

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

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How to Filter a Dictionary Based on Keys in C# - Step by Step Examples