C# Stack<T>

Summary: in this tutorial, you will learn how to use the C# Stack<T> to store elements in a collection based on the last-in-first-out (LIFO) principle.

Introduction to the C# Stack<T> type

Suppose you have a stack of books on your desk. When you get a new book, you place it on top of the stack. The top book is always the one you can easily pick for reading.

When you want to read a book, you take the one from the top of the stack, revealing the next book below.

In this analogy, the stack of books represents a data structure where you add and remove books in a first-in-last-out order (LIFO). The first book that you place on the stack is the last one that you remove from the stack.

In C#, Stack<T> class works the same way as a stack of books. The Stack<T> has two main methods:

• Push() – places an item on the top of the stack.
• Pop() – removes the item from the top of the stack.

The Stack<T> also has the Count property that returns the number of elements of the stack.

Because the Stack<T> is a generic class, you store values of any type T in the stack.

C# Stack<T> example

The following example illustrates how to use the Stack<T> class to manage a stack of books:

using static System.Console;

var bookStack = new Stack<string>();

var titles = new List<string>{
    "C# Tutorial",
    "Mastering LINQ",
    "A Complete Guide to EF Core"
};

// push
foreach (var title in titles)
{
    WriteLine($"Push the book '{title}' onto the stack.");
    bookStack.Push(title);
}
WriteLine($"The stack has {bookStack.Count} book(s).");

// pop
while (bookStack.Count > 0)
{
    var title = bookStack.Pop();
    WriteLine($"Pop the book '{title}' out of the stack.");
}

WriteLine($"The stack has {bookStack.Count} book(s).");Code language: C# (cs)

Output:

Push the book 'C# Tutorial' onto the stack.
Push the book 'Mastering LINQ' onto the stack.
Push the book 'A Complete Guide to EF Core' onto the stack.
The stack has 3 book(s).
Pop the book 'A Complete Guide to EF Core' out of the stack.
Pop the book 'Mastering LINQ' out of the stack.
Pop the book 'C# Tutorial' out of the stack.
The stack has 0 book(s).Code language: plaintext (plaintext)

How it works.

First, create a new stack that stores the strings representing the book titles:

var bookStack = new Stack<string>();Code language: C# (cs)

Second, initialize a list of book titles:

var titles = new List<string>{
    "C# Tutorial",
    "Mastering LINQ",
    "A Complete Guide to EF Core"
};Code language: C# (cs)

Third, iterate over the book titles and push each of them onto the stack using a foreach loop and Push() method:

foreach (var title in titles)
{
    WriteLine($"Push the book '{title}' onto the stack.");
    bookStack.Push(title);
}Code language: C# (cs)

Fourth, check the stack’s size using the Count property:

WriteLine($"The stack has {bookStack.Count} book(s).");Code language: C# (cs)

Fifth, remove each book from the stack using the Pop() method until the stack is empty:

while (bookStack.Count > 0)
{
    var title = bookStack.Pop();
    WriteLine($"Pop the book '{title}' out of the stack.");
}Code language: C# (cs)

Finally, shows the stack’s size:

WriteLine($"The stack has {bookStack.Count} book(s).");Code language: C# (cs)

Summary

• Use C# Stack<T> to manage a collection of elements in the last-in, first-out (LIFO) order.
• Use Push() method to push an element onto the stack.
• Use Pop() method to pop an element out of the stack.
• Use Count property to get the number of elements on the stack.