C# | Get an ICollection containing the keys in ListDictionary

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

Syntax:

public System.Collections.ICollection Keys { get; }

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

Below are the programs to illustrate the use of ListDictionary.Keys property:

Example 1:

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

class GFG {

    // Driver code
    public static void Main()
    {

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

        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");

        // Get an ICollection containing
        // the keys in the ListDictionary
        ICollection ic = myDict.Keys;

        // Displaying the keys in ICollection ic
        foreach(String str in ic)
        {
            Console.WriteLine(str);
        }
    }
}

Output:

Australia
Belgium
Netherlands
China
Russia
India

Example 2:

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

class GFG {

    // Driver code
    public static void Main()
    {

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

        myDict.Add("I", "first");
        myDict.Add("II", "second");
        myDict.Add("III", "third");
        myDict.Add("IV", "fourth");
        myDict.Add("V", "fifth");

        // Get an ICollection containing
        // the keys in the ListDictionary
        ICollection ic = myDict.Keys;

        // Displaying the keys in ICollection ic
        foreach(String str in ic)
        {
            Console.WriteLine(str);
        }
    }
}

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 ListDictionary. Therefore, changes to the ListDictionary 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.listdictionary.keys?view=netframework-4.7.2