C# 4 and .NET 4

Queue ❘ 237
Figure 10-1 shows the items of the queue. The Enqueue() method adds items to one end of the queue;
the items are read and removed at the other end of the queue with the Dequeue() method. Invoking the
Dequeue() method once more removes the next item from the queue.
Enqueue
figure 10-1
Dequeue
Methods of the Queue class are described in the following table.
seleCTed queue members
Count
Enqueue()
Dequeue()
Peek()
TrimExcess()
desCriPTion
The property Count returns the number of items in the queue.
The Enqueue() method adds an item to the end of the queue.
The Dequeue() method reads and removes an item from the head
of the queue. If there are no more items in the queue when the
Dequeue() method is invoked, an exception of type
InvalidOperationException is thrown.
The Peek() method reads an item from the head of the queue but
does not remove the item.
TrimExcess() resizes the capacity of the queue. The Dequeue()
method removes items from the queue, but it doesn’t resize the capacity
of the queue. To get rid of the empty items at the beginning of the
queue, use the TrimExcess() method.
When creating queues, you can use constructors similar to those used with the List type. The default
constructor creates an empty queue, but you can also use a constructor to specify the capacity. As items are
added to the queue, the capacity is increased to hold 4, 8, 16, and 32 items if the capacity is not defined.
Similarly to the List class, the capacity is always doubled as required. The default constructor of the
non-generic Queue class is different, because it creates an initial array of 32 empty items. With an overload
of the constructor, you can also pass any other collection that implements the IEnumerable interface
that is copied to the queue.
The sample application that demonstrates the use of the Queue class is a document management application.
One thread is used to add documents to the queue, and another thread reads documents from the
queue and processes them.
The items stored in the queue are of type Document. The Document class defines a title and content:
public class Document
{
public string Title { get; private set; }
public string Content { get; private set; }
}
public Document(string title, string content)
{
this.Title = title;
this.Content = content;
}
code snippet QueueSample/Document.cs
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