C# | Remove all elements 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.Clear Method is used to remove all elements from the Hashtable.

Syntax:

myTable.Clear()

Here myTable is the name of the Hashtable.

Exceptions: This method will give NotSupportedException if the Hashtable is read-only.

Example:

// C# code to remove all elements
// from the 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 all elements from Hashtable
        myTable.Clear();

        // 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 all elements from Hashtable
        myTable.Clear();

        // 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 : 0
Total number of entries in Hashtable : 3
Total number of entries in Hashtable : 0

Reference:

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