C# Stack

last modified October 5, 2026

This article introduces the generic Stack<T> collection in C#. A stack follows last-in, first-out (LIFO) order: the newest item is the first one removed.

Stack<T> is in System.Collections.Generic. Its main operations work at the top of the collection, making it useful for undo histories, parsing, and depth-first processing.

C# Stack example

Use Push to put a value on top of the stack. Enumeration starts at the top, so the values appear in reverse order from their insertion.

using System.Collections.Generic;

var pages = new Stack<string>();
pages.Push("home");
pages.Push("products");
pages.Push("details");

foreach (var page in pages)
{
    Console.WriteLine(page);
}

$ dotnet run
details
products
home

Peeking and popping

Peek reads the top value without removing it. Pop returns and removes the top value. The non-try methods throw InvalidOperationException if the stack is empty.

var values = new Stack<int>();
values.Push(4);
values.Push(8);
values.Push(12);

Console.WriteLine($"Top: {values.Peek()}");
Console.WriteLine($"Removed: {values.Pop()}");
Console.WriteLine($"Count: {values.Count}");

$ dotnet run
Top: 12
Removed: 12
Count: 2

Use TryPeek or TryPop when an empty stack is possible. They report whether an item was available instead of throwing.

var undo = new Stack<string>();
undo.Push("rename file");

if (undo.TryPop(out string? action))
{
    Console.WriteLine($"Undo {action}");
}

if (!undo.TryPop(out _))
{
    Console.WriteLine("No more actions");
}

$ dotnet run
Undo rename file
No more actions

Initializing and clearing a stack

A stack can be initialized from a sequence. The first sequence element becomes the bottom item, and the final element becomes the top item. Clear removes all items.

var numbers = new Stack<int>(new[] { 1, 2, 3 });
Console.WriteLine(numbers.Pop());

numbers.Clear();
Console.WriteLine(numbers.Count);

$ dotnet run
3
0

When to use a stack

A stack fits tasks where the most recent item should be handled first, such as traversing a tree depth-first or keeping a sequence of undo operations. Use Queue<T> instead when items must be processed in arrival order. Stack operations at the top are typically constant time.

Source

Stack<T> Class - .NET API

This article introduced the LIFO stack collection in C#.

Author

Jan Bodnar writes programming tutorials and educational content.

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