C# | Check if the Hashtable contains a specific Key

Last Updated : 11 Jul, 2025

The Hashtable class represents a collection of key-and-value pairs that are organized based on the hash code of the key. The key is used to access the items in the collection. Hashtable.ContainsKey(Object) Method is used to check whether the Hashtable contains a specific key or not. Syntax:

public virtual bool ContainsKey(object key);

Parameter:

key: The key of type System.Object to locate in the Hashtable.

Return Type: It return true if the Hashtable contains an element with the specified key otherwise, false. The return type of this method is System.Boolean. Exception: This method can give ArgumentNullException if the key is null. Below given are some examples to understand the implementation in a better way: Example 1:

CSHARP

// C# code to check if the HashTable
// contains a specific key
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Hashtable
        Hashtable myTable = new Hashtable();

        // Adding elements in Hashtable
        myTable.Add("g", "geeks");
        myTable.Add("c", "c++");
        myTable.Add("d", "data structures");
        myTable.Add("q", "quiz");

        // check if the HashTable contains
        // the required key or not.
        if (myTable.ContainsKey("c"))
            Console.WriteLine("myTable contains the key");
        else
            Console.WriteLine("myTable doesn't contain the key");
    }
}

Output:

myTable contains the key

Example 2:

CSHARP

// C# code to check if the HashTable
// contains a specific key
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Hashtable
        Hashtable myTable = new Hashtable();

        // Adding elements in Hashtable
        myTable.Add("India", "Country");
        myTable.Add("Chandigarh", "City");
        myTable.Add("Mars", "Planet");
        myTable.Add("China", "Country");

        // check if the HashTable contains
        // the required key or not.
        if (myTable.ContainsKey("Earth"))
            Console.WriteLine("myTable contains the key");
        else
            Console.WriteLine("myTable doesn't contain the key");
    }
}