C# | Remove all elements from the ArrayList

ArrayList represents an ordered collection of an object that can be indexed individually. It is basically an alternative to an array. It also allows dynamic memory allocation, adding, searching and sorting items in the list. ArrayList.Clear method is used to remove all the elements from the ArrayList.

Properties:

• Elements can be added or removed from the Array List collection at any point in time.
• The ArrayList is not guaranteed to be sorted.
• The capacity of an ArrayList is the number of elements the ArrayList can hold.
• Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.
• It also allows duplicate elements.
• Using multidimensional arrays as elements in an ArrayList collection is not supported.

Syntax:

public virtual void Clear ();

Exceptions: This method will give NotSupportedException if the ArrayList is read-only or the ArrayList has a fixed size.

Note:

• This method is an O(n) operation, where n is Count.
• Count is set to zero, and references to other objects from elements of the collection are also released.
• Capacity remains unchanged.

Below programs illustrate the use of ArrayList.Clear Method:

Example 1 :

// C# code to remove all elements
// from an ArrayList
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList(10);

        // Adding elements to ArrayList
        myList.Add("A");
        myList.Add("B");
        myList.Add("C");
        myList.Add("D");
        myList.Add("E");
        myList.Add("F");

        // Displaying the elements in ArrayList
        Console.WriteLine("Number of elements in ArrayList initially : "
                                                        + myList.Count);

        // Removing all elements from ArrayList
        myList.Clear();

        // Displaying the elements in ArrayList
        // after Removing all the elements
        Console.WriteLine("Number of elements in ArrayList : " + myList.Count);
    }
}

Output:

Number of elements in ArrayList initially : 6
Number of elements in ArrayList : 0

Example 2:

// C# code to remove all elements
// from an ArrayList
using System;
using System.Collections;


class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList(10);

        // Adding elements to ArrayList
        myList.Add(3);
        myList.Add(5);
        myList.Add(7);
        myList.Add(9);
        myList.Add(11);

        // Displaying the elements in ArrayList
        Console.WriteLine("Number of elements in ArrayList initially : "
                                                        + myList.Count);

        // Removing all elements from ArrayList
        myList.Clear();

        // Displaying the elements in ArrayList
        // after Removing all the elements
        Console.WriteLine("Number of elements in ArrayList : " + myList.Count);
    }
}

Output:

Number of elements in ArrayList initially : 5
Number of elements in ArrayList : 0

Reference:

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