Queue.Dequeue Method ()

 

Removes and returns the object at the beginning of the Queue.

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

Public Overridable Function Dequeue As Object

Return Value

Type: System.Object

The object that is removed from the beginning of the Queue.

Exception Condition
InvalidOperationException

The Queue is empty.

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

null can be added to the Queue as a value. To distinguish between a null value and the end of the Queue, check the Count property or catch the InvalidOperationException, which is thrown when the Queue is empty.

This method is an O(1) operation.

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

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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