Remove a key from a Dictionary in C#

This post will discuss how to remove a key from a Dictionary in C#.

1. Using `Dictionary<TKey,TValue>.Remove()` Method

The standard solution to remove a value with the specified key from a dictionary is using the Dictionary<TKey,TValue>.Remove() method. The following example uses the Remove() method to remove a key-value pair from a dictionary.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

Dictionary<string, int> dict = new Dictionary<string, int>() {

{"A", 1}, {"B", 2}, {"C", 3}, {"D", 4}

};

var keyToRemove = "D";

dict.Remove(keyToRemove);

Console.WriteLine(String.Join(", ", dict)); // [A, 1], [B, 2], [C, 3]

}

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The Remove() method returns true if the key is successfully removed from the dictionary and false if the key is not found in the dictionary, as the following example illustrates.

using System;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

Dictionary<string, int> dict = new Dictionary<string, int>() {

{"A", 1}, {"B", 2}, {"C", 3}, {"D", 4}

};

var keyToRemove = "D";

if (dict.Remove(keyToRemove)) {

Console.WriteLine("Key removed from the Dictionary");

} else {

Console.WriteLine("Dictionary doesn't contain the Key");

}

Console.WriteLine(String.Join(", ", dict)); // [A, 1], [B, 2], [C, 3]

}

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2. Using LINQ

To avoid any modifications to the existing dictionary, you can use LINQ to construct a new dictionary instance without the desired key-value pairs. The following code example shows how to remove the specified collection of keys from a dictionary.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

Dictionary<string, int> dict = new Dictionary<string, int>() {

{"A", 1}, {"B", 2}, {"C", 3}, {"D", 4}

};

HashSet<string> keysToRemove = new HashSet<string> {"A", "C"};

var filteredDict = dict.Where(kvp => !keysToRemove.Contains(kvp.Key))

.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

Console.WriteLine(String.Join(", ", filteredDict)); // [B, 2], [D, 4]

}

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That’s all about removing a key from a Dictionary in C#.

Remove a key from a Dictionary in C#

1. Using Dictionary<TKey,TValue>.Remove() Method

2. Using LINQ

1. Using `Dictionary<TKey,TValue>.Remove()` Method