C# | Get an enumerator that iterates through the Dictionary

Dictionary<TKey, TValue>.GetEnumerator method is used to return an enumerator that iterates through the Dictionary<TKey, TValue>.

Syntax:

public System.Collections.Generic.Dictionary<TKey,TValue>.Enumerator GetEnumerator ();

Return Value: This method returns an Dictionary<TKey, TValue>.Enumerator structure for the Dictionary<TKey, TValue>.

Below programs illustrate the use of Dictionary<TKey, TValue>.GetEnumerator Method:

Example 1:

// C# code to get an IDictionaryEnumerator
// that iterates through the Dictionary
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Dictionary named myDict
        Dictionary<string, string> myDict =
           new Dictionary<string, string>();

        myDict.Add("Australia", "Canberra");
        myDict.Add("Belgium", "Brussels");
        myDict.Add("Netherlands", "Amsterdam");
        myDict.Add("China", "Beijing");
        myDict.Add("Russia", "Moscow");
        myDict.Add("India", "New Delhi");

        // To get an IDictionaryEnumerator
        // for the Dictionary
        IDictionaryEnumerator myEnumerator =
                     myDict.GetEnumerator();

        // If MoveNext passes the end of the
        // collection, the enumerator is positioned
        // after the last element in the collection
        // and MoveNext returns false.
        while (myEnumerator.MoveNext())
            Console.WriteLine(myEnumerator.Key + " --> "
                              + myEnumerator.Value);
    }
}

Output:

Australia --> Canberra
Belgium --> Brussels
Netherlands --> Amsterdam
China --> Beijing
Russia --> Moscow
India --> New Delhi

Example 2:

// C# code to get an IDictionaryEnumerator
// that iterates through the Dictionary
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Dictionary named myDict
        Dictionary<string, string> myDict =
           new Dictionary<string, string>();

        // Adding key/value pairs in myDict
        myDict.Add("I", "C");
        myDict.Add("II", "C++");
        myDict.Add("III", "Java");
        myDict.Add("IV", "Python");
        myDict.Add("V", "C#");

        // To get an IDictionaryEnumerator
        // for the Dictionary
        IDictionaryEnumerator myEnumerator =
                     myDict.GetEnumerator();

        // If MoveNext passes the end of the
        // collection, the enumerator is positioned
        // after the last element in the collection
        // and MoveNext returns false.
        while (myEnumerator.MoveNext())
            Console.WriteLine(myEnumerator.Key + " --> "
                              + myEnumerator.Value);
    }
}

Output:

I --> C
II --> C++
III --> Java
IV --> Python
V --> C#

Note:

• The foreach statement of the C# language hides the complexity of the enumerators. Therefore, using foreach is recommended, instead of directly manipulating the enumerator.
• Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.
• Current returns the same object until either MoveNext or Reset is called. MoveNext sets Current to the next element.
• An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and its behavior is undefined.
• This method is an O(1) operation.

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2.getenumerator?view=netframework-4.7.2