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Stack.Push Method

Inserts an object at the top of the Stack.

Namespace:  System.Collections
Assembly:  mscorlib (in mscorlib.dll)

public virtual void Push(
	Object obj
)

Parameters

obj
Type: System.Object
The Object to push onto the Stack. The value can be null.

Stack is implemented as a circular buffer.

If Count already equals the capacity, the capacity of the Stack is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added.

null can be pushed onto the Stack as a placeholder, if needed. It occupies a slot in the stack and is treated like any object.

If Count is less than the capacity of the stack, Push is an O(1) operation. If the capacity needs to be increased to accommodate the new element, Push becomes an O(n) operation, where n is Count.

The following example shows how to add elements to the Stack, remove elements from the Stack, or view the element at the top of the Stack.


 using System;
 using System.Collections;
 public class SamplesStack  {

    public static void Main()  {

       // Creates and initializes a new Stack.
       Stack myStack = new Stack();
       myStack.Push( "The" );
       myStack.Push( "quick" );
       myStack.Push( "brown" );
       myStack.Push( "fox" );

       // Displays the Stack.
       Console.Write( "Stack values:" );
       PrintValues( myStack, '\t' );

       // Removes an element from the Stack.
       Console.WriteLine( "(Pop)\t\t{0}", myStack.Pop() );

       // Displays the Stack.
       Console.Write( "Stack values:" );
       PrintValues( myStack, '\t' );

       // Removes another element from the Stack.
       Console.WriteLine( "(Pop)\t\t{0}", myStack.Pop() );

       // Displays the Stack.
       Console.Write( "Stack values:" );
       PrintValues( myStack, '\t' );

       // Views the first element in the Stack but does not remove it.
       Console.WriteLine( "(Peek)\t\t{0}", myStack.Peek() );

       // Displays the Stack.
       Console.Write( "Stack values:" );
       PrintValues( myStack, '\t' );
    }


    public static void PrintValues( IEnumerable myCollection, char mySeparator )  {
       foreach ( Object obj in myCollection )
          Console.Write( "{0}{1}", mySeparator, obj );
       Console.WriteLine();
    }

 }


 /* 
 This code produces the following output.

 Stack values:    fox    brown    quick    The
 (Pop)        fox
 Stack values:    brown    quick    The
 (Pop)        brown
 Stack values:    quick    The
 (Peek)        quick
 Stack values:    quick    The
 */ 



.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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