C# | Remove the element with the specified key from the Hashtable

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.Remove(Object) Method is used to remove the element with the specified key from the Hashtable.

Syntax:

public virtual void Remove (object key);

Parameter:

key: It is the key of the element to remove of type System.Object.

Exceptions:

• ArgumentNullException: If the key is null.
• NotSupportedException: If the Hashtable is read-only or has a fixed size.

Example:

// C# code to remove the element
// with the specified key from Hashtable
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("2", "Even & Prime");
        myTable.Add("3", "Odd & Prime");
        myTable.Add("4", "Even & non-prime");
        myTable.Add("9", "Odd & non-prime");

        // Print the number of entries in Hashtable
        Console.WriteLine("Total number of entries in Hashtable : "
                                                  + myTable.Count);

        // To remove the elements from Hashtable
        // which has key as "3"
        myTable.Remove("3");

        // Print the number of entries in Hashtable
        Console.WriteLine("Total number of entries in Hashtable : "
                                                  + myTable.Count);

        // To remove the elements from Hashtable
        // which has key as "4"
        myTable.Remove("4");

        // Print the number of entries in Hashtable
        Console.WriteLine("Total number of entries in Hashtable : "
                                                  + myTable.Count);

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

        // Print the number of entries in Hashtable
        Console.WriteLine("Total number of entries in Hashtable : "
                                                  + myTable.Count);

        // To remove the elements from Hashtable
        // which has key as "c"
        myTable.Remove("c");

        // Print the number of entries in Hashtable
        Console.WriteLine("Total number of entries in Hashtable : "
                                                  + myTable.Count);
    }
}

Output:

Total number of entries in Hashtable : 4
Total number of entries in Hashtable : 3
Total number of entries in Hashtable : 2
Total number of entries in Hashtable : 5
Total number of entries in Hashtable : 4

Reference:

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