Get an enumerator that iterates through the ListDictionary in C#

To get an enumerator that iterates through the ListDictionary, you can use the GetEnumerator() method, which returns an IDictionaryEnumerator. This allows you to iterate through the key-value pairs in the dictionary using a while loop or foreach loop.

The ListDictionary is a specialized collection class that implements a dictionary using a singly linked list, making it efficient for small collections (typically 10 or fewer elements).

Syntax

Following is the syntax for getting an enumerator from a ListDictionary −

IDictionaryEnumerator enumerator = listDictionary.GetEnumerator();
while (enumerator.MoveNext()) {
   // Access enumerator.Key and enumerator.Value
}

You can also use a foreach loop with DictionaryEntry −

foreach (DictionaryEntry entry in listDictionary) {
   // Access entry.Key and entry.Value
}

Using GetEnumerator() with IDictionaryEnumerator

The GetEnumerator() method returns an IDictionaryEnumerator that provides access to both keys and values −

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

public class Demo {
   public static void Main() {
      ListDictionary dict = new ListDictionary();
      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("ListDictionary key-value pairs using GetEnumerator():");
      IDictionaryEnumerator demoEnum = dict.GetEnumerator();
      while (demoEnum.MoveNext()) {
         Console.WriteLine("Key = " + demoEnum.Key + ", Value = " + demoEnum.Value);
      }
   }
}

The output of the above code is −

ListDictionary key-value pairs using GetEnumerator():
Key = A, Value = Books
Key = B, Value = Electronics
Key = C, Value = Smart Wearables
Key = D, Value = Pet Supplies
Key = E, Value = Clothing
Key = F, Value = Footwear

Using foreach with DictionaryEntry

An alternative approach is to use a foreach loop with DictionaryEntry, which internally uses the enumerator −

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");
      
      Console.WriteLine("ListDictionary elements using foreach:");
      foreach (DictionaryEntry entry in dict) {
         Console.WriteLine(entry.Key + " = " + entry.Value);
      }
   }
}

The output of the above code is −

ListDictionary elements using foreach:
1 = One
2 = Two
3 = Three
4 = Four
5 = Five

Comparison of Iteration Methods

Conclusion

The GetEnumerator() method provides an IDictionaryEnumerator for manually iterating through a ListDictionary. For simpler code, you can use a foreach loop with DictionaryEntry, which internally uses the same enumerator mechanism.