Queue<T> & Stack<T>

Syntax

Queue<Type> queue = new Queue<Type>();\nStack<Type> stack = new Stack<Type>();

Examples

Queue<string> line = new Queue<string>();
line.Enqueue("Customer A");
line.Enqueue("Customer B");
line.Enqueue("Customer C");

Console.WriteLine(line.Dequeue());  // Customer A - first in, first out
Console.WriteLine(line.Peek());      // Customer B - look without removing
Console.WriteLine(line.Count);        // 2

Stack<string> history = new Stack<string>();
history.Push("Page 1");
history.Push("Page 2");
history.Push("Page 3");

Console.WriteLine(history.Pop());  // Page 3 - last in, first out
Console.WriteLine(history.Peek());  // Page 2 - look without removing

bool IsBalanced(string input)
{
    Stack<char> stack = new Stack<char>();
    foreach (char c in input)
    {
        if (c == '(') stack.Push(c);
        else if (c == ')')
        {
            if (stack.Count == 0) return false;
            stack.Pop();
        }
    }
    return stack.Count == 0;
}

Console.WriteLine(IsBalanced("(a(b)c)"));  // true
Console.WriteLine(IsBalanced("(a(b)c"));    // false

Best practices

• Use Queue<T> for FIFO processing like task scheduling or breadth-first traversal, and Stack<T> for LIFO needs like undo history or depth-first traversal
• Use Peek() to inspect the next item without removing it, and TryDequeue()/TryPop() to avoid an exception when the collection might be empty
• Prefer these purpose-built types over a List<T> with manual Insert(0, ...) or RemoveAt(list.Count - 1) - they are clearer in intent and more efficient
• Remember both are still generic collections (Queue<T>, Stack<T>) - specify the element type just like with List<T>

At a glance

Purpose

Applications on the .NET platform

File extension

.cs

Runs in

.NET runtime

Usually used with

.NET SDK and libraries

Specifications & further reading

• C# language reference

Related C# documentation