Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Export (0) Print
Expand All

Queue::Dequeue Method

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

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

public:
virtual Object^ Dequeue()

Return Value

Type: System::Object
The object that is removed from the beginning of the Queue.

ExceptionCondition
InvalidOperationException

The Queue is empty.

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

nullptr 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.

using namespace System;
using namespace System::Collections;
void PrintValues( IEnumerable^ myCollection );
int main()
{

   // Creates and initializes a new Queue.
   Queue^ myQ = gcnew 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)\t{0}", myQ->Dequeue() );

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

   // Removes another element from the Queue.
   Console::WriteLine( "(Dequeue)\t{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)   \t{0}", myQ->Peek() );

   // Displays the Queue.
   Console::Write( "Queue values:" );
   PrintValues( myQ );
}

void PrintValues( IEnumerable^ myCollection )
{
   IEnumerator^ myEnum = myCollection->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ obj = safe_cast<Object^>(myEnum->Current);
      Console::Write( "    {0}", obj );
   }

   Console::WriteLine();
}

/* 
 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

 */

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

Community Additions

ADD
Show:
© 2015 Microsoft