C# | Remove all objects from the Stack

Stack represents a last-in, first out collection of object. It is used when you need a last-in, first-out access to items. When you add an item in the list, it is called pushing the item and when you remove it, it is called popping the item. Stack<T>.Clear Method is used to Removes all objects from the Stack<T>. This method is an O(n) operation, where n is Count.

Properties:

• The capacity of a Stack is the number of elements the Stack can hold. As elements are added to a Stack, the capacity is automatically increased as required through reallocation.
• If Count is less than the capacity of the stack, Push is an O(1) operation. If the capacity needs to be increased to accommodate the new element, Push becomes an O(n) operation, where n is Count. Pop is an O(1) operation.
• Stack accepts null as a valid value and allows duplicate elements.

Syntax:

public virtual void Clear();

Below given are some examples to understand the implementation in a better way.

Example 1:

// C# code to Remove all
// objects from the Stack
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Stack of strings
        Stack<string> myStack = new Stack<string>();

        // Inserting the elements into the Stack
        myStack.Push("1st Element");
        myStack.Push("2nd Element");
        myStack.Push("3rd Element");
        myStack.Push("4th Element");
        myStack.Push("5th Element");
        myStack.Push("6th Element");

        // Displaying the count of elements
        // contained in the Stack before
        // removing all the elements
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        // Removing all elements from Stack
        myStack.Clear();

        // Displaying the count of elements
        // contained in the Stack after
        // removing all the elements
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);
    }
}

Output:

Total number of elements in the Stack are : 6
Total number of elements in the Stack are : 0

Example 2:

// C# code to Remove all
// objects from the Stack
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Stack of Integers
        Stack<int> myStack = new Stack<int>();

        // Inserting the elements into the Stack
        myStack.Push(3);
        myStack.Push(5);
        myStack.Push(7);
        myStack.Push(9);
        myStack.Push(11);

        // Displaying the count of elements
        // contained in the Stack before
        // removing all the elements
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        // Removing all elements from Stack
        myStack.Clear();

        // Displaying the count of elements
        // contained in the Stack after
        // removing all the elements
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);
    }
}

Output:

Total number of elements in the Stack are : 5
Total number of elements in the Stack are : 0

Reference:

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