Remove entry with specified key from OrderedDictionary in C#

The OrderedDictionary class in C# provides the Remove() method to remove entries with a specified key. The OrderedDictionary maintains the insertion order of elements while allowing both key-based and index-based access.

Syntax

Following is the syntax for removing an entry by key from an OrderedDictionary −

orderedDictionary.Remove(key);

Parameters

• key ? The key of the entry to remove from the OrderedDictionary.

Return Value

The Remove() method does not return a value. It removes the entry if the key exists, or does nothing if the key is not found.

Example - Removing a Single Entry

The following example demonstrates removing one entry from an OrderedDictionary −

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

public class Demo {
   public static void Main() {
      OrderedDictionary dict = new OrderedDictionary();
      dict.Add("A", "Books");
      dict.Add("B", "Electronics");
      dict.Add("C", "Smart Wearables");
      dict.Add("D", "Pet Supplies");
      dict.Add("E", "Clothing");
      dict.Add("F", "Footwear");
      
      Console.WriteLine("OrderedDictionary elements...");
      foreach(DictionaryEntry d in dict) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
      Console.WriteLine("Count of elements in OrderedDictionary = " + dict.Count);
      
      dict.Remove("E");
      
      Console.WriteLine("Count of elements in OrderedDictionary (Updated)= " + dict.Count);
   }
}

The output of the above code is −

OrderedDictionary elements...
A Books
B Electronics
C Smart Wearables
D Pet Supplies
E Clothing
F Footwear
Count of elements in OrderedDictionary = 6
Count of elements in OrderedDictionary (Updated)= 5

Example - Removing Multiple Entries

The following example demonstrates removing multiple entries from an OrderedDictionary −

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

public class Demo {
   public static void Main() {
      OrderedDictionary dict = new OrderedDictionary();
      dict.Add("A", "One");
      dict.Add("B", "Two");
      dict.Add("C", "Three");
      dict.Add("D", "Four");
      
      Console.WriteLine("OrderedDictionary elements...");
      foreach(DictionaryEntry d in dict) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
      Console.WriteLine("Count of elements in OrderedDictionary = " + dict.Count);
      
      dict.Remove("C");
      dict.Remove("D");
      
      Console.WriteLine("Count of elements in OrderedDictionary (Updated)= " + dict.Count);
      
      Console.WriteLine("Remaining elements...");
      foreach(DictionaryEntry d in dict) {
         Console.WriteLine(d.Key + " " + d.Value);
      }
   }
}

The output of the above code is −

OrderedDictionary elements...
A One
B Two
C Three
D Four
Count of elements in OrderedDictionary = 4
Count of elements in OrderedDictionary (Updated)= 2
Remaining elements...
A One
B Two

Key Points

• The Remove() method removes the first occurrence of the specified key.

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

• After removal, the insertion order of remaining elements is maintained.

• The Count property is automatically updated after removal.

Conclusion

The Remove() method provides an efficient way to remove entries from an OrderedDictionary by specifying the key. The method maintains the insertion order of remaining elements and automatically updates the collection's count property.