C# Stack.Pop() Method

The Stack<T>.Pop() method in C# removes and returns the element that was added most recently. Since a stack follows the Last-In, First-Out (LIFO) principle, Pop() removes the next element in LIFO order.

• It returns and removes an element from the stack.
• The Count of the stack decreases by one after a successful Pop() operation.

using System;
using System.Collections.Generic;

class GFG{
    
    public static void Main(){
        
        Stack<string> myStack = new Stack<string>();

        myStack.Push("One");
        myStack.Push("Two");
        myStack.Push("Three");
        myStack.Push("Four");

        Console.WriteLine("Number of elements: " + myStack.Count);

        string removedElement = myStack.Pop();

        Console.WriteLine("Removed element: " + removedElement);
        Console.WriteLine("Number of elements after Pop(): "
                          + myStack.Count);
    }
}

Number of elements: 4
Removed element: Four
Number of elements after Pop(): 3

Explanation: "Four" was the most recently added element, so Pop() returns and removes it. As a result, the number of elements decreases from 4 to 3.

Syntax

public T Pop();

• Return Value: The Pop() method returns the element of type T that is removed from the Stack<T>.
• Exception: Pop() throws an InvalidOperationException if the stack is empty. Therefore, check the Count property before calling Pop() when the stack may be empty.

How Pop() Works

Suppose a stack contains the following elements:

three <- Next to be removed
two
one

Calling:

myStack.Pop();

removes and returns "three". The stack then becomes:

two
one

Pop() on an Empty Stack

Calling Pop() on an empty stack throws an InvalidOperationException.

Stack<int> myStack = new Stack<int>();
Console.WriteLine(myStack.Pop());

Runtime Error:

System.InvalidOperationException: Stack empty.

To avoid this exception:

if (myStack.Count > 0){
Console.WriteLine(myStack.Pop());
}
else
{
Console.WriteLine("Stack is empty.");
}

Pop() vs Peek()