Programming C# 3.0, 5th Edition

Queues

A queue represents a first-in, first-out (FIFO) collection. The classic analogy is to a line (or queue, if you are British) at a ticket window. The first person in line ought to be the first person to come off the line to buy a ticket.

A queue is a good collection to use when you are managing a limited resource. For example, you might want to send messages to a resource that can handle only one message at a time. You would then create a message queue so that you can say to your clients: "Your message is important to us. Messages are handled in the order in which they are received."

The Queue class has a number of member methods and properties, as shown in Table 9-4.

Table 9-4. Queue methods and properties

Method or property	Purpose
Count	Public property that gets the number of elements in the Queue
Clear( )	Removes all objects from the Queue
Contains( )	Determines whether an element is in the Queue
CopyTo( )	Copies the Queue elements to an existing one-dimensional array
Dequeue( )	Removes and returns the object at the beginning of the Queue
Enqueue( )	Adds an object to the end of the Queue
GetEnumerator( )	Returns an enumerator for the Queue
Peek( )	Returns the object at the beginning of the Queue without removing it
ToArray( )	Copies the elements to a new array
TrimExcess( )	Reduces the current queue's capacity to the actual number of elements in the list

You add elements to your queue with the Enqueue command, and take them off the queue with Dequeue or by using an enumerator. Example 9-16 illustrates. ...