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Queue.Enqueue Method

Adds an object to the end of the Queue.

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

'Declaration
Public Overridable Sub Enqueue ( _
	obj As Object _
)

Parameters

obj
Type: System.Object
The object to add to the Queue. The value can be Nothing.

The capacity of a Queue is the number of elements the Queue can hold. As elements are added to a Queue, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize.

The growth factor is the number by which the current capacity is multiplied when a greater capacity is required. The growth factor is determined when the Queue is constructed. The capacity of the Queue will always increase by a minimum value, regardless of the growth factor; a growth factor of 1.0 will not prevent the Queue from increasing in size.

If Count is less than the capacity of the internal array, this method is an O(1) operation. If the internal array needs to be reallocated to accommodate the new element, this method becomes an O(n) operation, where n is Count.

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


Imports System
Imports System.Collections
Imports Microsoft.VisualBasic


Public Class SamplesQueue


    Public Shared Sub Main()

        ' Creates and initializes a new Queue.
        Dim myQ As New Queue()
        myQ.Enqueue("The")
        myQ.Enqueue("quick")
        myQ.Enqueue("brown")
        myQ.Enqueue("fox")

        ' Displays the Queue.
        Console.Write("Queue values:")
        PrintValues(myQ)

        ' Removes an element from the Queue.
        Console.WriteLine("(Dequeue)    {0}", myQ.Dequeue())

        ' Displays the Queue.
        Console.Write("Queue values:")
        PrintValues(myQ)

        ' Removes another element from the Queue.
        Console.WriteLine("(Dequeue)    {0}", myQ.Dequeue())

        ' Displays the Queue.
        Console.Write("Queue values:")
        PrintValues(myQ)

        ' Views the first element in the Queue but does not remove it.
        Console.WriteLine("(Peek)       {0}", myQ.Peek())

        ' Displays the Queue.
        Console.Write("Queue values:")
        PrintValues(myQ)
    End Sub 'Main

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

End Class 'SamplesQueue


' This code produces the following output.
' 
' Queue values:    The    quick    brown    fox
' (Dequeue)    The
' Queue values:    quick    brown    fox
' (Dequeue)    quick
' Queue values:    brown    fox
' (Peek)       brown
' Queue values:    brown    fox



.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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