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Queue(T).Peek Method

Returns the object at the beginning of the Queue(T) without removing it.

Namespace:  System.Collections.Generic
Assemblies:   System.Collections (in System.Collections.dll)
  System (in System.dll)

member Peek : unit -> 'T 

Return Value

Type: T
The object at the beginning of the Queue(T).

ExceptionCondition
InvalidOperationException

The Queue(T) is empty.

This method is similar to the Dequeue method, but Peek does not modify the Queue(T).

If type T is a reference type, a null reference (Nothing in Visual Basic) can be added to the Queue(T) as a value.

This method is an O(1) operation.

The following code example demonstrates several methods of the Queue(T) generic class, including the Peek method.

The code example creates a queue of strings with default capacity and uses the Enqueue method to queue five strings. The elements of the queue are enumerated, which does not change the state of the queue. The Dequeue method is used to dequeue the first string. The Peek method is used to look at the next item in the queue, and then the Dequeue method is used to dequeue it.

The ToArray method is used to create an array and copy the queue elements to it, then the array is passed to the Queue(T) constructor that takes IEnumerable(T), creating a copy of the queue. The elements of the copy are displayed.

An array twice the size of the queue is created, and the CopyTo method is used to copy the array elements beginning at the middle of the array. The Queue(T) constructor is used again to create a second copy of the queue containing three null elements at the beginning.

The Contains method is used to show that the string "four" is in the first copy of the queue, after which the Clear method clears the copy and the Count property shows that the queue is empty.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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