使用Service Bus Topic 实现简单的聊天室

创建Service Bus能够參照：
https://azure.microsoft.com/en-gb/documentation/articles/service-bus-dotnet-how-to-use-topics-subscriptions/
Azure Service Bus做广播和消息通知功能非常合适，而且能够订阅不同的Topic（不同的消息类型或不同的聊天室）。

1. 首先须要安装Azure Service Bus的nuget package：



2. 建议安装Azure Service Explorer来查看Service bus中创建的Q或者Topic（本文主要介绍Topic）
https://code.msdn.microsoft.com/windowsazure/Service-Bus-Explorer-f2abca5a
非常好用。而且开源，能够学习。

3. 实现过程

3.1 首先创建1个Winform程序，拖两个button和两个Textbox。界面例如以下：



3.2 创建1个类，叫ChatClient：

public class ChatClient
{
private string ConnStr
{
get
{
return CloudConfigurationManager.GetSetting("Microsoft.ServiceBus.ConnectionString");
}
}

private const string topicName = "TestTopic";
public OnMsgRecieved OnMsgRecieved;

public void Subscribe(string subscriber)
{
var td = new TopicDescription(topicName)
{
MaxSizeInMegabytes = 5120,
DefaultMessageTimeToLive = new TimeSpan(0, 1, 0)
};

// Create a new Topic with custom settings
string connectionString =
CloudConfigurationManager.GetSetting("Microsoft.ServiceBus.ConnectionString");

var namespaceManager =
NamespaceManager.CreateFromConnectionString(connectionString);

if (!namespaceManager.TopicExists(topicName))
{
namespaceManager.CreateTopic(td);
}

if (!namespaceManager.SubscriptionExists(topicName, subscriber))
{
namespaceManager.CreateSubscription(topicName, subscriber);
}

SubscriptionClient Client = SubscriptionClient.CreateFromConnectionString
(ConnStr, topicName, subscriber, ReceiveMode.PeekLock);

// Configure the callback options
OnMessageOptions options = new OnMessageOptions();
options.AutoComplete = false;
options.AutoRenewTimeout = TimeSpan.FromMinutes(1);

Task.Run(() =>
{
Client.OnMessage((message) =>
{
try
{
// Process message from subscription
OnMsgRecieved(string.Format("{0}:{1}",
message.Properties["name"], message.GetBody<string>()));
}
catch (Exception)
{
// Indicates a problem, unlock message in subscription
message.Abandon();
}
}, options);
});

}

private TopicClient _topicClient;

public TopicClient TopicClient
{
get
{
if (_topicClient == null)
{
_topicClient = TopicClient.CreateFromConnectionString(ConnStr, topicName);
}

return _topicClient;
}
}

public void SendMsg(string name, string msg)
{
var message = new BrokeredMessage(msg);
message.Properties["name"] = name;
TopicClient.Send(message);
}

}

1. 代码包括了Subscribe和SendMsg两个方法，注意name用于标识client的。假设两个client给一样的名字，仅仅有client1个client能收到消息。

2. 我Hard Code了Topic名称，假设须要实现多种消息广播。给不同的名字就能够了

3. 这行代码：

SubscriptionClient Client = SubscriptionClient.CreateFromConnectionString
(ConnStr, topicName, subscriber, ReceiveMode.PeekLock);

中的ReceiveMode包括两种：PeekLock和ReceiveAndDelete ，前者加锁拿消息放回，后者拿消息并删除。

4. TopicClient不必每次都创建。是支持多线程环境的。

5.

var td = new TopicDescription(topicName)
{
MaxSizeInMegabytes = 5120,
DefaultMessageTimeToLive = new TimeSpan(0, 1, 0)
};

这里设置了消息的最大长度和默认生命周期，可依据场景进行配置。

Winform的UI逻辑代码相对简单：

public partial class Form1 : Form
{
ChatClient cc = new ChatClient();

public Form1()
{
InitializeComponent();
cc.OnMsgRecieved = (msg) =>
{
SetText(msg);
};
}

private void btnSend_Click(object sender, EventArgs e)
{
cc.SendMsg(txtName.Text, txtMsg.Text);
}

delegate void SetTextCallback(string text);

private void SetText(string text)
{
if (txtResult.InvokeRequired)
{
var d = new SetTextCallback(SetText);
Invoke(d, new object[] { text });
}
else
{
txtResult.Text += "\r\n" + text;
}
}

private void btnSaveName_Click(object sender, EventArgs e)
{
cc.Subscribe(txtName.Text);
}
}

逻辑非常easy，点击SaveName。又一次订阅。点Send按钮，发送消息。

须要注意的就是跨线程訪问UI控件，这里你须要一个delegate。

实现截图：