How to Remove a Key-Value Pair from a Dictionary in C#

How to Remove a Key-Value Pair from a Dictionary in C# ?

Answer

To remove a key-value pair from a dictionary in C#, you can use the `Remove` method of the `Dictionary` class from the `System.Collections.Generic` namespace. This method removes the element with the specified key from the dictionary.


✐ Examples

1 Removing a Key-Value Pair Using the `Remove` Method

We can remove a key-value pair from a dictionary in C# using the `Remove` method. This example demonstrates how to remove a key-value pair by specifying the key and print the dictionary contents before and after the removal.

For example,

  1. We start by including the necessary namespace: using System.Collections.Generic;.
  2. We declare and initialize a dictionary named myDictionary with integer keys and string values.
  3. We print the dictionary contents before removing a key-value pair.
  4. We use the `Remove` method to remove a key-value pair by specifying the key.
  5. We print the dictionary contents after removing the key-value pair.

C# Program

using System;
using System.Collections.Generic;

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

        // Print the dictionary contents before removal
        Console.WriteLine("Dictionary contents before removal:");
        foreach (KeyValuePair<int, string> kvp in myDictionary)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }

        // Key to remove
        int keyToRemove = 2;

        // Remove the key-value pair using the Remove method
        myDictionary.Remove(keyToRemove);

        // Print the dictionary contents after removal
        Console.WriteLine("Dictionary contents after removal:");
        foreach (KeyValuePair<int, string> kvp in myDictionary)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

Dictionary contents before removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
Dictionary contents after removal:
Key: 1, Value: One
Key: 3, Value: Three

2 Checking for Key Existence Before Removing Using `Remove` Method

We can check if a key exists before attempting to remove a key-value pair in a dictionary in C# using the `Remove` method. This example demonstrates how to check for key existence and remove the key-value pair if it exists, then print the dictionary contents before and after the removal.

For example,

  1. We start by including the necessary namespace: using System.Collections.Generic;.
  2. We declare and initialize a dictionary named myDictionary with integer keys and string values.
  3. We print the dictionary contents before removing a key-value pair.
  4. We check if the key exists and use the `Remove` method to remove the key-value pair if it exists.
  5. We print the dictionary contents after removing the key-value pair.

C# Program

using System;
using System.Collections.Generic;

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

        // Print the dictionary contents before removal
        Console.WriteLine("Dictionary contents before removal:");
        foreach (KeyValuePair<int, string> kvp in myDictionary)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }

        // Key to remove
        int keyToRemove = 4;

        // Check if the key exists and remove it if it does
        if (myDictionary.ContainsKey(keyToRemove))
        {
            myDictionary.Remove(keyToRemove);
            Console.WriteLine("Key {0} was removed from the dictionary.", keyToRemove);
        }
        else
        {
            Console.WriteLine("Key {0} does not exist in the dictionary.", keyToRemove);
        }

        // Print the dictionary contents after removal
        Console.WriteLine("Dictionary contents after removal:");
        foreach (KeyValuePair<int, string> kvp in myDictionary)
        {
            Console.WriteLine("Key: {0}, Value: {1}", kvp.Key, kvp.Value);
        }
    }
}

Output

Dictionary contents before removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
Key 4 does not exist in the dictionary.
Dictionary contents after removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three

Summary

In this tutorial, we learned How to Remove a Key-Value Pair from a Dictionary in C# language with well detailed examples.


More C# Dictionaries Tutorials

  1. How to create an Empty Dictionary in C# ?
  2. How to create a Dictionary with Initial Key-Value Pairs in C# ?
  3. How to Print a Dictionary in C# ?
  4. How to Add a Key-Value Pair to a Dictionary in C# ?
  5. How to Set a Default Value for a Key in a Dictionary in C# ?
  6. How to Update the Value for a Key in a Dictionary in C# ?
  7. How to Check if a Dictionary is Empty in C# ?
  8. How to Check if a Key Exists in a Dictionary in C# ?
  9. How to Check if a Value Exists in a Dictionary in C# ?
  10. How to Get the Value Associated with a Key in a Dictionary in C# ?
  11. How to Remove a Key-Value Pair from a Dictionary in C# ?
  12. How to Remove Key-Value Pairs from a Dictionary Based on Values in C# ?
  13. How to Clear all Key-Value Pairs from a Dictionary in C# ?
  14. How to Iterate over Keys in a Dictionary in C# ?
  15. How to Iterate over Values in a Dictionary in C# ?
  16. How to Iterate over Entries (Key-Value Pairs) in a Dictionary in C# ?
  17. How to Get the Size (Number of Key-Value Pairs) of a Dictionary in C# ?
  18. How to Convert a Dictionary to an Array of Keys in C# ?
  19. How to Convert a Dictionary to an Array of Values in C# ?
  20. How to Convert a Dictionary to an Array of Key-Value Pairs in C# ?
  21. How to Merge Two Dictionaries in C# ?
  22. How to Clone a Dictionary in C# ?
  23. How to Check if Two Dictionaries are Equal in C# ?
  24. How to Sort a Dictionary by Keys in C# ?
  25. How to Sort a Dictionary by Values in C# ?
  26. How to Filter a Dictionary Based on Keys in C# ?
  27. How to Filter a Dictionary Based on Values in C# ?
  28. How to Reduce Values in a Dictionary to a Single Value in C# ?
  29. How to Convert an Array of Key-Value Pairs to a Dictionary in C# ?
  30. How to Convert a Dictionary to a JSON String in C# ?
  31. How to Convert a JSON String to a Dictionary in C# ?
  32. How to Swap Keys and Values in a Dictionary in C# ?
  33. How to Create a Dictionary of Dictionaries in C# ?
  34. How to Iterate Over a Dictionary of Dictionaries in C# ?