C#集合之队列的用法

        //存储在队列中的元素是Document类型
          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;
            }
          }
          
        //DocumentManager类是Queue<Document>外面的一层。用来如何将文档添加到队列和从队列中获取文档
          public class DocumentManager
          {
            private readonly Queue<Document> documentQueue = new Queue<Document>();

            //因为多个线程访问DocumentManager类，所以用lock语句锁定对队列的访问
            
            public void AddDocument(Document doc)
            {
              lock (this)
              {
                documentQueue.Enqueue(doc);
              }
            }

            public Document GetDocument()
            {
              Document doc = null;
              lock (this)
              {
                if (this.IsDocumentAvailable)
                    doc = documentQueue.Dequeue();
              }
              return doc;
            }

            public bool IsDocumentAvailable
            {
              get
              {
                lock (this)
                {
                    return documentQueue.Count > 0;
                }
                        
              }
            }
          }
          
         //使用ProcessDocuments类在一个单独的任务中读取和删除队列中的文档。
          public class ProcessDocuments
          {
            //能从外部访问的唯一方法是Start()方法
            //在Start()中，实例化一个新任务。创建一个ProcessDocuments对象，调用ProcessDocuments的Run()方法
            public static void Start(DocumentManager dm)
            {
              Task.Factory.StartNew(new ProcessDocuments(dm).Run);
            }

            protected ProcessDocuments(DocumentManager dm)
            {
              if (dm == null)
                throw new ArgumentNullException("dm");
              documentManager = dm;
            }

            private DocumentManager documentManager;

            //定义一个无限循环，使用DocumentManager类的IsDocumentAvailable属性确定队列中是否还有文档。
            protected void Run()
            {
              while (true)
              {
                if (documentManager.IsDocumentAvailable)
                {
                  Document doc = documentManager.GetDocument();
                  if(doc != null)
                    Console.WriteLine("Processing document {0}", doc.Title);
                }
                Thread.Sleep(new Random().Next(20));
              }
            }
          }

　　　　　　static void Main()
            {
                var dm = new DocumentManager();

                ProcessDocuments.Start(dm);
                ProcessDocuments.Start(dm);
                // Create documents and add them to the DocumentManager
                for (int i = 0; i < 1000; i++)
                {
                    Document doc = new Document("Doc " + i.ToString(), "content");
                    dm.AddDocument(doc);
                    Console.WriteLine("Added document {0}", doc.Title);
                    Thread.Sleep(new Random().Next(20));
                }

                Console.ReadKey();
            }