Programming C#, Third 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 only handle 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
Synchronized( )	Public static method that returns a Queue wrapper that is thread-safe.
Count	Public property that gets the number of elements in the Queue.
IsSynchronized	Public property to get a value indicating if the Queue is synchronized.
SyncRoot	Public property that returns an object that can be used to synchronize access to the Queue.
Clear( )	Removes all objects from the Queue.
Clone( )	Creates a shallow copy.
Contains( )	Determines if 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( )