C# | Get an ICollection containing the keys in HybridDictionary

HybridDictionary.Keys property is used to get an ICollection containing the keys in the HybridDictionary.

Syntax:

public System.Collections.ICollection Keys { get; }

Return Value: It returns an ICollection containing the keys in the HybridDictionary.

Below programs illustrate the use of HybridDictionary.Keys Property:

Example 1:

// C# code to get an ICollection containing
// the keys in the HybridDictionary.
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a HybridDictionary named myDict
        HybridDictionary myDict = new HybridDictionary();

        // Adding key/value pairs in myDict
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
        myDict.Add("E", "Elephant");
        myDict.Add("F", "Fish");

        // Creating a String arr named myArr
        String[] myArr = new String[myDict.Count];

        // copying the Keys in HybridDictionary
        // to a one-dimensional Array instance
        // at the specified index.
        myDict.Keys.CopyTo(myArr, 0);

        // To get an ICollection containing
        // the keys in the HybridDictionary
        for (int i = 0; i < myDict.Count; i++)
            Console.WriteLine(myArr[i]);
    }
}

Output:

A
B
C
D
E
F

Example 2:

// C# code to get an ICollection containing
// the keys in the HybridDictionary.
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a HybridDictionary named myDict
        HybridDictionary myDict = new HybridDictionary();

        // Adding key/value pairs in myDict
        myDict.Add("I", "first");
        myDict.Add("II", "second");
        myDict.Add("III", "third");
        myDict.Add("IV", "fourth");
        myDict.Add("V", "fifth");

        // Creating a String arr named myArr
        String[] myArr = new String[myDict.Count];

        // copying the Keys in HybridDictionary
        // to a one-dimensional Array instance
        // at the specified index.
        myDict.Keys.CopyTo(myArr, 0);

        // To get an ICollection containing
        // the keys in the HybridDictionary
        for (int i = 0; i < myDict.Count; i++)
            Console.WriteLine(myArr[i]);
    }
}

Output:

I
II
III
IV
V

Note:

• The order of the values in the ICollection is unspecified, but it is the same order as the associated values in the ICollection returned by the Values method.
• The returned ICollection is not a static copy. Instead, the ICollection refers back to the keys in the original HybridDictionary. Therefore, changes to the HybridDictionary continue to be reflected in the ICollection.
• Retrieving the value of this property is an O(1) operation.

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.specialized.hybriddictionary.keys?view=netframework-4.7.2