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Stack.Pop Method

Removes and returns the object at the top of the Stack.

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

'Declaration
Public Overridable Function Pop As Object
'Usage
Dim instance As Stack 
Dim returnValue As Object 

returnValue = instance.Pop()

Return Value

Type: System.Object
The Object removed from the top of the Stack.

ExceptionCondition
InvalidOperationException

The Stack is empty.

This method is similar to the Peek method, but Peek does not modify the Stack.

Nothing can be pushed onto the Stack as a placeholder, if needed. To distinguish between a null value and the end of the stack, check the Count property or catch the InvalidOperationException, which is thrown when the Stack is empty.

Stack is implemented as a circular buffer. This method is an O(1) operation.

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.

Imports System
Imports System.Collections
Imports Microsoft.VisualBasic

Public Class SamplesStack    

    Public Shared Sub Main()

        ' Creates and initializes a new Stack. 
        Dim myStack As New Stack()
        myStack.Push("The")
        myStack.Push("quick")
        myStack.Push("brown")
        myStack.Push("fox")

        ' Displays the Stack.
        Console.Write("Stack values:")
        PrintValues(myStack, ControlChars.Tab)

        ' Removes an element from the Stack.
        Console.WriteLine("(Pop)" & ControlChars.Tab & ControlChars.Tab & _
           "{0}", myStack.Pop())

        ' Displays the Stack.
        Console.Write("Stack values:")
        PrintValues(myStack, ControlChars.Tab)

        ' Removes another element from the Stack.
        Console.WriteLine("(Pop)" & ControlChars.Tab & ControlChars.Tab & _
           "{0}", myStack.Pop())

        ' Displays the Stack.
        Console.Write("Stack values:")
        PrintValues(myStack, ControlChars.Tab)

        ' Views the first element in the Stack but does not remove it.
        Console.WriteLine("(Peek)" & ControlChars.Tab & ControlChars.Tab & _
           "{0}", myStack.Peek())

        ' Displays the Stack.
        Console.Write("Stack values:")
        PrintValues(myStack, ControlChars.Tab)

    End Sub 

    Public Shared Sub PrintValues(myCollection As IEnumerable, mySeparator As Char)
        Dim obj As [Object]
        For Each obj In  myCollection
            Console.Write("{0}{1}", mySeparator, obj)
        Next obj
        Console.WriteLine()
    End Sub 'PrintValues

End Class 'SamplesStack


' 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

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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