C# | How to get hash code for the specified key of a Hashtable

Hashtable.GetHash(Object) method is used to get the hashcode of the specified key of a Hashtable object. This method is inherited from the Object Class.

Syntax:

protected virtual int GetHash(Object Key);

Exception: This method will give NullReferenceException if the key is null.

Below programs illustrate the use of above-discussed method:

Example 1:

// C# Program to illustrate the
// Hashtable.GetHash(Object) method
using System;
using System.Collections;

// Inheriting Hashtable as
// Hashtable.GetHash(Object)
// method is protected method
class HashCode : Hashtable {

    // Main Method
    static void Main(string[] args)
    {

        // creating object for HashCode as
        // to access protected methods we
        // have to create object for the
        // derived class
        HashCode h = new HashCode();

        // Add Elements into Hashtable
        h.Add("1001", "Parek Shetty");
        h.Add("1002", "Deshmuk Narayan");
        h.Add("1003", "Ratan Kaalikaran");

        ICollection Key = h.Keys;

        foreach(string val in Key)
        {

            // printing Hashtable
            Console.Write(val + " : " + h[val]);
            Console.Write("\n");

            // printing hashcode with keys
            int hcode = h.GetHash(val);

            Console.Write(val + " : " + hcode);
            Console.Write("\n");
        }
    }
}

Output:

1002 : Deshmuk Narayan
1002 : 985757554
1001 : Parek Shetty
1001 : -1708895167
1003 : Ratan Kaalikaran
1003 : -1892225314

Example 2:

// C# Program to illustrate the
// Hashtable.GetHash(Object) method
using System;
using System.Collections;

class HashCode : Hashtable {

    // Main Method
    static void Main(string[] args)
    {
        HashCode h = new HashCode();

        // Adding elements
        h.Add('A', "Pritam Devadhya");
        h.Add('B', "Arjun Balachi");
        h.Add('C', "Timanad Panigrahi");

        ICollection Key = h.Keys;

        int hcode = h.GetHash('C');

        Console.Write("HashCode: " + hcode);
    }
}

Output:

HashCode: 4390979

Reference:

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