Mastering C# Stack: Push, Pop, and Practical Examples

What Is a Stack in C#?

A stack is a collection that follows the Last‑In, First‑Out (LIFO) principle. Think of a stack of books: only the top book can be removed. The same logic applies to the .NET Stack class—elements are added on top with Push and removed from the top with Pop.

Declaring a Stack

Instantiate a stack with the new keyword and assign it to a variable.

Stack st = new Stack();

Adding Elements – Push

The Push method places a new element on top of the stack.

st.Push(1);

Removing Elements – Pop

The Pop method removes and returns the topmost element.

var top = st.Pop();

Other Common Operations

• Count – Retrieves the number of items in the stack.

  int total = st.Count;

• Contains – Checks if a specific value exists.

  bool hasThree = st.Contains(3);

Hands‑On Example 1: Using Push, Count, and Contains

Below is a console application that demonstrates stack creation, element insertion, enumeration, and basic queries.

using System;
using System.Collections;

namespace DemoApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            // 1. Create a new stack
            Stack st = new Stack();

            // 2. Push three integers onto the stack
            st.Push(1);
            st.Push(2);
            st.Push(3);

            // 3. Enumerate the stack – note the LIFO order
            foreach (Object obj in st)
            {
                Console.WriteLine(obj);
            }

            // 4. Output the total count
            Console.WriteLine($"\nNumber of elements: {st.Count}");

            // 5. Check if the stack contains the value 3
            Console.WriteLine($"Does stack contain 3? {st.Contains(3)}");

            Console.ReadKey();
        }
    }
}

Explanation

1. We declare a Stack named st.
2. Three integers are pushed; the last pushed (3) becomes the topmost element.
3. Using foreach enumerates the stack from top to bottom, displaying 3, 2, 1.
4. Count returns 3, confirming three items.
5. Contains(3) returns true, proving that 3 is present.

Running this program yields the following output:

Hands‑On Example 2: Removing the Top Element with Pop

Here’s a concise illustration of the Pop method in action.

using System;
using System.Collections;

namespace DemoApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            Stack st = new Stack();
            st.Push(1);
            st.Push(2);
            st.Push(3);

            // Remove the top element (3)
            st.Pop();

            foreach (Object obj in st)
            {
                Console.WriteLine(obj);
            }

            Console.ReadKey();
        }
    }
}

Explanation

1. After pushing 1, 2, and 3, the stack top is 3.
2. Calling Pop() removes 3, leaving 2 and 1.
3. The enumeration prints 2 followed by 1.

Output of the program:

Key Takeaways

• A Stack operates on LIFO.
• Use Push to add and Pop to remove the top element.
• Additional helpers: Count for size, Contains for membership checks.