C# 5.0 Programmer's Reference

332 ❘ CHAPTER 14 Collection Classes
You can also think of a stack as a stack of papers on a desk. You can add things on the top and take
them off of the top, but you can’t pull papers out of the middle or the bottom of the stack without
the whole thing toppling over.
Normally, you use the Stack class’s Push and Pop methods to add and remove items from a stack,
but the class also provides a few methods that let you cheat by peeking at the top item without
removing it or by converting the Stack into an array.
The following table describes the Stack class’s most useful properties and methods.
Property/Method
Clear
Contains
CopyTo
Count
Peek
Pop
Push
ToArray
Purpose
Removes all the items.
Returns true if the Stack contains a particular object.
Copies some or all of the Stack’s objects into a onedimensional
array.
Returns the number of items in the Stack.
Returns a reference to the Stack class’s top item without removing it
from the Stack.
Returns the Stack class’s top item and removes it from the Stack.
Adds an item to the top of the Stack.
Returns a one-dimensional array containing references to the objects
in the Stack. The Stack class’s top item is placed first in the array.
A Stack allocates memory to store its items. If you Push an object onto a Stack that is completely
full, the Stack must resize itself to make more room and that slows things down.
Like the Hashtable class, the Stack class provides overloaded constructors that let you determine
how much memory should initially be allocated. The first constructor takes no parameters and
allocates a default amount of memory.
The second constructor takes as a parameter the number of items the Stack should initially hold.
If you know that you will add 10,000 items to the Stack, you can avoid a lot of resizing by initially
allocating room for 10,000 items.
The third version of the constructor takes as a parameter an object that implements the ICollection
interface. The constructor allocates enough room to hold the items in the ICollection and copies
them into the Stack.
The following short example demonstrates a Stack.
Stack stack = new Stack();
stack.Push("Apple");
stack.Push("Banana");
stack.Push("Cherry");
Console.WriteLine(stack.Pop());
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