Get an ICollection containing the keys in HybridDictionary in C#

To get an ICollection containing the keys in HybridDictionary, you use the Keys property. The HybridDictionary class is part of the System.Collections.Specialized namespace and provides a collection that uses a ListDictionary for small collections and switches to a Hashtable for larger collections automatically.

The Keys property returns an ICollection that contains all the keys in the dictionary, which can then be iterated over or copied to an array.

Syntax

Following is the syntax for accessing the Keys property −

ICollection keys = hybridDictionary.Keys;

To copy keys to an array −

string[] keysArray = new string[hybridDictionary.Count];
hybridDictionary.Keys.CopyTo(keysArray, 0);

Using Keys.CopyTo() Method

The following example demonstrates copying keys to an array using the CopyTo() method −

using System;
using System.Collections.Specialized;

public class Demo {
    public static void Main() {
        HybridDictionary dict = new HybridDictionary();
        dict.Add("One", "Katie");
        dict.Add("Two", "Andy");
        dict.Add("Three", "Gary");
        dict.Add("Four", "Mark");
        dict.Add("Five", "Marie");
        dict.Add("Six", "Sam");
        dict.Add("Seven", "Harry");
        dict.Add("Eight", "Kevin");
        dict.Add("Nine", "Ryan");
        
        String[] strArr = new String[dict.Count];
        dict.Keys.CopyTo(strArr, 0);
        
        Console.WriteLine("Keys in HybridDictionary:");
        for (int i = 0; i < dict.Count; i++)
            Console.WriteLine(strArr[i]);
    }
}

The output of the above code is −

Keys in HybridDictionary:
Eight
Seven
Four
Three
One
Five
Six
Two
Nine

Using foreach with Keys Collection

You can also iterate directly over the Keys collection using a foreach loop −

using System;
using System.Collections.Specialized;

public class Demo {
    public static void Main() {
        HybridDictionary dict = new HybridDictionary();
        dict.Add("1", "A");
        dict.Add("2", "B");
        dict.Add("3", "C");
        dict.Add("4", "D");
        dict.Add("5", "E");
        dict.Add("6", "F");
        
        Console.WriteLine("Keys using foreach:");
        foreach (string key in dict.Keys) {
            Console.WriteLine(key);
        }
        
        Console.WriteLine("\nTotal number of keys: " + dict.Keys.Count);
    }
}

The output of the above code is −

Keys using foreach:
1
2
3
4
5
6

Total number of keys: 6

Key Properties of HybridDictionary.Keys

Conclusion

The Keys property of HybridDictionary provides an ICollection containing all keys in the dictionary. You can access these keys by copying them to an array using CopyTo() or iterate through them directly using a foreach loop for flexible key manipulation.