C#: Using IDictionaryEnumerator with HashTable
Posted by: Suprotim Agarwal
in Category C# 2.0, 3.0 and 4.0
Abstract: In this article, we will see how to enumerate a HashTable using an IDictionaryEnumerator.
The IDictionaryEnumerator enumerates the elements of a non-generic dictionary like a HashTable. It is a strongly typed enumerator which inherits IEnumerator by adding three properties:
where Entry gets both the key and the value of the current dictionary entry in the form of a DictionaryEntry struct, Key gets the key of the current dictionary entry and Value gets the value of the current dictionary entry.
A HashTable collection stores a (Key, Value) pair and uses the Key to hash and obtain the storage location. Let us see how to enumerate a HashTable using an IDictionaryEnumerator
As you can see in the code above, we are using HashTable.GetEnumerator which iterates through the HashTable. Since the the enumerator is positioned before the first element in the collection, you must call the MoveNext method to advance the enumerator to the first element of the collection. When there are no more elements to read, MoveNext() returns false. The current value is obtained using Entry, Key and Value.
Note: You can also access items in the Dictionary using the generalized Entry property which returns a DictionaryEntry class type i.e. via ide.Entry.Key and ide.Entry.Value
While Enumerating a HashTable or a non-generic dictionary key value pair, use the IDictionaryEnumerator instead of the IEnumerator since the former gives you access to both the key and value of the current entry.
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The entire source code of this article can be downloaded over here