How to create a Stack in C#?

A Stack in C# is a generic collection that follows the Last-In-First-Out (LIFO) principle. Elements are added and removed from the top of the stack. The Stack<T> class is part of the System.Collections.Generic namespace and provides type-safe stack operations.

Syntax

Following is the syntax for creating a Stack −

Stack<T> stackName = new Stack<T>();

Common Stack operations −

stack.Push(item);    // Add element to top
T item = stack.Pop(); // Remove and return top element
T item = stack.Peek(); // Return top element without removing
bool exists = stack.Contains(item); // Check if element exists

How Stack Works

Creating and Using a Stack

Basic Stack Operations

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      Stack<int> stack = new Stack<int>();
      stack.Push(100);
      stack.Push(150);
      stack.Push(175);
      stack.Push(200);
      stack.Push(225);
      stack.Push(250);
      stack.Push(300);
      stack.Push(400);
      stack.Push(450);
      stack.Push(500);
      Console.WriteLine("Elements in the Stack:");
      foreach(var val in stack) {
         Console.WriteLine(val);
      }
      Console.WriteLine("Count of elements in the Stack = " + stack.Count);
      Console.WriteLine("Does Stack has the element 400? = " + stack.Contains(400));
   }
}

The output of the above code is −

Elements in the Stack:
500
450
400
300
250
225
200
175
150
100
Count of elements in the Stack = 10
Does Stack has the element 400? = True

Stack with Pop and Peek Operations

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      Stack<int> stack = new Stack<int>();
      stack.Push(10);
      stack.Push(20);
      stack.Push(30);
      stack.Push(40);
      stack.Push(50);
      
      Console.WriteLine("Original Stack Count: " + stack.Count);
      Console.WriteLine("Top element (Peek): " + stack.Peek());
      Console.WriteLine("Count after Peek: " + stack.Count);
      
      Console.WriteLine("Popped element: " + stack.Pop());
      Console.WriteLine("Count after Pop: " + stack.Count);
      
      Console.WriteLine("Remaining elements:");
      foreach (int res in stack) {
         Console.WriteLine(res);
      }
   }
}

The output of the above code is −

Original Stack Count: 5
Top element (Peek): 50
Count after Peek: 5
Popped element: 50
Count after Pop: 4
Remaining elements:
40
30
20
10

Common Stack Methods

Conclusion

The Stack<T> class in C# provides an efficient LIFO collection for managing elements. Use Push() to add elements, Pop() to remove them, and Peek() to examine the top element without removal. Stacks are ideal for scenarios like function call management, undo operations, and expression evaluation.