C#队列学习笔记：RabbitMQ实现客户端相互通讯

    一、引言

    fanout类型的Exchange，路由规则非常简单：它会把所有发送到该Exchange的消息，路由到所有与它绑定的Queue中。假设有一个聊天室，各个客户端都订阅在同一fanout exchange type，那每个客户端发送出来的消息，所有的客户端都能收到，因为大家都订阅了。此时，只需要简单地限制一下，只有是与我有关的消息，才在聊天界面上显示。这样，即可达到相互通讯的效果。

    二、示例

    2.1、环境准备

    本示例使用EasyNetQ来实现，请先在NuGet上安装。

    2.2、实体类

    新建一个实体类MessageBody：

    public class MessageBody
    {
        public string FromUserId { get; set; }
        public string Message { get; set; }
        public string ToUserId { get; set; }
    }

    2.3、主窗体

    新建一个ChatMain窗体：

    代码如下：

    public partial class ChatMain : Form
    {
        public ChatMain()
        {
            InitializeComponent();
        }

        /// 

        /// 客户端 A
        /// 
        /// 
        /// 
        private void Button1_Click(object sender, EventArgs e)
        {
            ChatWith chatWith = new ChatWith(currentUserId: "UserA")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();
        }

        /// 

        /// 客户端 B
        /// 
        /// 
        /// 
        private void Button2_Click(object sender, EventArgs e)
        {
            ChatWith chatWith = new ChatWith(currentUserId: "UserB")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();
        }

        /// 

        /// 客户端 C
        /// 
        /// 
        /// 
        private void Button3_Click(object sender, EventArgs e)
        {

            ChatWith chatWith = new ChatWith(currentUserId: "UserC")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();

        }

        /// 

        /// 客户端 D
        /// 
        /// 
        /// 
        private void Button4_Click(object sender, EventArgs e)
        {
            ChatWith chatWith = new ChatWith(currentUserId: "UserD")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();
        }
    }

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    2.4、客户端窗体

    新建一个ChatWith窗体：

    代码如下：

    public partial class ChatWith : Form
    {
        public delegate void ChatWithDelegate();
        public delegate void ChatWithDelegate(T1 obj1);
        public delegate void ChatWithDelegate(T1 obj1, T2 obj2);

        public string CurrentUserId { get; }

        private IBus bus;
        public const string ConnStringMQ = "host=192.168.2.242:5672,192.168.2.165:5672;virtualHost=/;username=hello;password=world";
        public const string FanoutExchange = "fanoutEC";

        /// 

        /// 有参构造函数
        /// 
        /// 
        public ChatWith(string currentUserId)
        {
            InitializeComponent();

            //在多线程程序中，新创建的线程不能访问UI线程创建的窗口控件。
            //此时若想访问窗体的控件，可将窗体构造函数中的CheckForIllegalCrossThreadCalls设置为false。
            //这时线程就能安全地访问窗体控件了。
            CheckForIllegalCrossThreadCalls = false;

            CurrentUserId = currentUserId;
        }

        /// 

        /// ShowMessage重载
        /// 
        /// 
        private void ShowMessage(string msg)
        {
            if (InvokeRequired)//InvokeRequired：当前线程不是创建控件的线程时为true
            {
                BeginInvoke(new ChatWithDelegate<string>(ShowMessage), msg);
            }
            else
            {
                ListViewItem item = new ListViewItem(new string[] { DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), msg });
                lvwReceiveMsg.Items.Insert(0, item);
            }
        }

        /// 

        /// ShowMessage重载
        /// 
        /// 
        /// 
        private void ShowMessage(string toUserId, string msg)
        {
            if (InvokeRequired)
            {
                BeginInvoke(new ChatWithDelegate<string, string>(ShowMessage), toUserId, msg);
            }
            else
            {
                ListViewItem item = new ListViewItem(new string[] { DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), toUserId, msg });
                lvwReceiveMsg.Items.Insert(0, item);
            }
        }

        /// 

        /// 绑定队列并订阅
        /// 
        /// 
        /// 
        private void ChatWith_Load(object sender, EventArgs e)
        {
            cmbOnLine.SelectedIndex = 0;
            Text = Text + $"[{CurrentUserId}]";

            //这里不能使用using，否则订阅者立即就释放了，订阅不到消息。
            bus = RabbitHutch.CreateBus(ConnStringMQ);
            {
                if (bus.IsConnected)
                {
                    var exchange = bus.Advanced.ExchangeDeclare(name: FanoutExchange, type: ExchangeType.Fanout);
                    var queue = bus.Advanced.QueueDeclare(name: $"{FanoutExchange}_queue_{CurrentUserId}");
                    bus.Advanced.Bind(exchange: exchange, queue: queue, routingKey: "");

                    bus.Advanced.Consume(queue, registration =>
                    {
                        registration.Add((message, info) =>
                        {
                            if (message.Body.ToUserId == CurrentUserId)
                            {
                                ShowMessage(message.Body.FromUserId, message.Body.Message);
                            }
                        });
                    });
                }
                else
                {
                    ShowMessage("服务器连接失败。");
                }
            }
        }

        /// 

        /// 发送
        /// 
        /// 
        /// 
        private void btnSend_Click(object sender, EventArgs e)
        {
            try
            {
                using (var bus = RabbitHutch.CreateBus(ConnStringMQ))
                {
                    if (bus.IsConnected)
                    {
                        if (cmbOnLine.Text == "*")//群发
                        {
                            foreach (var item in cmbOnLine.Items.Cast<string>().Where(s => s != "*" && s != CurrentUserId))
                            {
                                var exchange = bus.Advanced.ExchangeDeclare(name: FanoutExchange, type: ExchangeType.Fanout);
                                var messageBody = new MessageBody
                                {
                                    FromUserId = CurrentUserId,
                                    Message = txtSendMsg.Text,
                                    ToUserId = item
                                };
                                bus.Advanced.Publish(exchange: exchange,
                                    routingKey: "",
                                    mandatory: false,
                                    message: new Message(messageBody));
                            }
                        }
                        else//私聊
                        {
                            var exchange = bus.Advanced.ExchangeDeclare(name: FanoutExchange, type: ExchangeType.Fanout);
                            var messageBody = new MessageBody
                            {
                                FromUserId = CurrentUserId,
                                Message = txtSendMsg.Text,
                                ToUserId = cmbOnLine.Text
                            };
                            bus.Advanced.Publish(exchange: exchange,
                                routingKey: "",
                                mandatory: false,
                                message: new Message(messageBody));
                        }
                    }
                    else
                    {
                        ShowMessage("发送消息失败。");
                    }
                }
            }
            catch (Exception ex)
            {
                ShowMessage(ex.Message);
            }
        }

        /// 

        /// 关闭
        /// 
        /// 
        /// 
        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }

        /// 

        /// 窗体关闭事件
        /// 
        /// 
        /// 
        private void ChatWith_FormClosed(object sender, FormClosedEventArgs e)
        {
            bus?.Dispose();
        }
    }

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    2.5、运行结果