Remove the entry with specified key from ListDictionary in C#

The ListDictionary class in C# provides the Remove() method to delete entries by their key. This method removes the key-value pair associated with the specified key from the dictionary and returns no value.

Syntax

Following is the syntax for removing an entry from a ListDictionary −

listDictionary.Remove(key);

Parameters

• key − The key of the entry to remove from the ListDictionary.

Return Value

The Remove() does not return a value. It simply removes the specified key-value pair if the key exists.

Using Remove() Method

Here's how to remove a single entry from a ListDictionary −

using System;
using System.Collections;
using System.Collections.Specialized;

public class Demo {
   public static void Main(){
      ListDictionary dict1 = new ListDictionary();
      dict1.Add("A", "Books");
      dict1.Add("B", "Electronics");
      dict1.Add("C", "Smart Wearables");
      dict1.Add("D", "Pet Supplies");
      dict1.Add("E", "Clothing");
      dict1.Add("F", "Footwear");
      
      Console.WriteLine("ListDictionary1 elements...");
      foreach(DictionaryEntry d in dict1) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
      
      ListDictionary dict2 = new ListDictionary();
      dict2.Add("1", "One");
      dict2.Add("2", "Two");
      dict2.Add("3", "Three");
      dict2.Add("4", "Four");
      dict2.Add("5", "Five");
      dict2.Add("6", "Six");
      
      Console.WriteLine("\nListDictionary2 elements...");
      foreach(DictionaryEntry d in dict2) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
      
      Console.WriteLine("Count of key/value pairs in Dictionary 2 = " + dict2.Count);
      dict2.Remove("4");
      Console.WriteLine("Count of key/value pairs in Dictionary 2 (Updated) = " + dict2.Count);
   }
}

The output of the above code is −

ListDictionary1 elements...
A Books
B Electronics
C Smart Wearables
D Pet Supplies
E Clothing
F Footwear

ListDictionary2 elements...
1 One
2 Two
3 Three
4 Four
5 Five
6 Six
Count of key/value pairs in Dictionary 2 = 6
Count of key/value pairs in Dictionary 2 (Updated) = 5

Removing Multiple Entries

You can remove multiple entries by calling the Remove() method for each key −

using System;
using System.Collections;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      ListDictionary dict = new ListDictionary();
      dict.Add("1", "One");
      dict.Add("2", "Two");
      dict.Add("3", "Three");
      dict.Add("4", "Four");
      dict.Add("5", "Five");
      dict.Add("6", "Six");
      
      Console.WriteLine("ListDictionary elements...");
      foreach(DictionaryEntry d in dict) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
      
      Console.WriteLine("Count of key/value pairs in Dictionary = " + dict.Count);
      dict.Remove("2");
      dict.Remove("3");
      dict.Remove("4");
      Console.WriteLine("Count of key/value pairs in Dictionary (Updated) = " + dict.Count);
      
      Console.WriteLine("\nRemaining elements...");
      foreach(DictionaryEntry d in dict) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
   }
}

The output of the above code is −

ListDictionary elements...
1 One
2 Two
3 Three
4 Four
5 Five
6 Six
Count of key/value pairs in Dictionary = 6
Count of key/value pairs in Dictionary (Updated) = 3

Remaining elements...
1 One
5 Five
6 Six

Key Rules

• If the specified key does not exist, the Remove() method does nothing and no exception is thrown.

• The method removes both the key and its associated value from the dictionary.

• After removal, the Count property reflects the updated number of entries.

• Keys are compared using case-sensitive comparison by default.

Conclusion

The Remove() method in ListDictionary provides a simple way to delete entries by their key. It safely handles non-existent keys without throwing exceptions and automatically updates the dictionary's count after successful removal.