原文:

    ASP.NET SignalR 是为 ASP.NET 开发人员提供的一个库，可以简化开发人员将实时 Web 功能添加到应用程序的过程。实时 Web 功能是指这样一种功能：当所连接的客户端变得可用时服务器代码可以立即向其推送内容，而不是让服务器等待客户端请求新的数据。

    下面介绍一下本人在Android手机开发中的使用，开发编译环境使用Xamarin。手机作为一个客户端接入服务器。

     首先，在Xamarin中建立Android App，添加SignalR Client开发包，目前最新版本为2.2.0.0。

     然后，添加FireHub类。FireHub类的实现代码如下：

using System;using System.Collections.Generic;using System.Text;using System.ComponentModel;using Microsoft.AspNet.SignalR;using Microsoft.AspNet.SignalR.Client;using Microsoft.AspNet.SignalR.Client.Hubs;using NicoDemo.Model;namespace Nico.Android.SignalR{	public class FireHub	{		#region 变量声明		public HubConnection _connection=null;		private IHubProxy _proxy=null;		public bool IsConnected = false;		public delegate void ReceiveMessageDelegate(string msg);		public event ReceiveMessageDelegate Receive=null;		public delegate void HubCloseDelegate();		public event HubCloseDelegate CloseHub = null;		public delegate void HubStatusChangedDelegate(int state,string msg);		public event HubStatusChangedDelegate StateChanged = null;		public delegate void AddWebMessageDelegate(WebMessage wm);		public event AddWebMessageDelegate AddWebMessage = null;		#endregion		#region 初始化		public FireHub()		{			IsConnected = false;			_connection = null;			_proxy = null;		}		public string Dispose()		{			try			{				if (_connection != null)				{					try					{						_connection.Stop();					}					catch					{					}					_connection = null;				}				if (_proxy != null)					_proxy = null;				IsConnected = false;				return "";			}			catch(Exception err)			{				return string.Format("({0}-{1})",err.Message + err.StackTrace);			}		}		#endregion		#region HUB事件		void _connection_Closed()		{			if (CloseHub != null)				CloseHub();			IsConnected = false;		}		void _connection_Received(string obj)		{			if (Receive != null)				Receive(obj);		}		#endregion		#region HUB客户端方法		public bool Connect(string url,int timeout=5000)		{			try			{				if (_connection == null)				{					_connection = new HubConnection(url);//,queryString);					_connection.Received += _connection_Received;					_connection.Closed += _connection_Closed;					_connection.StateChanged += _connection_StateChanged;					_proxy = _connection.CreateHubProxy("notifyHub");				}				if (_connection.Start().Wait(timeout))//同步调用				{					IsConnected = true;					return true;				}				else				{					IsConnected = false;					_connection.Dispose();					_connection = null;					_proxy = null;					return false;				}			}			catch			{				return false;			}		}		void _connection_StateChanged(StateChange obj)		{			try			{				switch (obj.NewState)				{				case ConnectionState.Disconnected:					IsConnected = false;					if (_connection != null)					{						_connection.Dispose();						_connection = null;						_proxy = null;					}					if (StateChanged != null)						StateChanged(0,"");					break;				}			}			catch(Exception err)			{				if (StateChanged != null)					StateChanged(1, "_connection_StateChanged:"+err.Message);                			}		}		public bool ConnectToServer(UsersEntity user,int timeout=5000)		{			try			{				if (_connection == null || _proxy == null||!IsConnected)					return false;				return _proxy.Invoke("connect",user.ID,user.Name,user.TypeID).Wait(timeout);			}			catch(Exception err)			{				if (StateChanged != null)					StateChanged(1, "ConnectToServer:"+err.Message);                				return false;			}		}		public bool SendMessageToAll(UsersEntity user,string message, int timeout = 5000)		{			try			{				if (_connection == null || _proxy == null || !IsConnected)					return false;				_proxy.Invoke("sendMessageToAll", user.ID,user.Name,user.TypeID,message);//.Wait(timeout);				return true;			}			catch(Exception err)			{				if (StateChanged != null)					StateChanged(1,"SendMessageToAll:"+ err.Message);                				return false;			}		}		public bool SendMessageToPrivate(string toConnID, string message)		{			try			{				if (_connection == null || _proxy == null || !IsConnected)					return false;				_proxy.Invoke("sendPrivateMessage", toConnID, message);				return true;			}			catch(Exception err)			{				if (StateChanged != null)					StateChanged(1, "SendMessageToPrivate:"+err.Message);                				return false;			}		}		#endregion		#region 公共函数		public bool SendToWeb(UsersEntity user,int timeout=5000)		{			try			{				//        事件时间				//事件类型				//发送者				//单位编号				//信息内容				if (!SendMessageToAll(user,"connect test", timeout))					return false;				return true;			}			catch (Exception err)			{				if (StateChanged != null)					StateChanged(1, "SendToWeb:"+err.Message);				return false;			}		}		#endregion	}	public class HubUser	{		[DisplayName("连接ID")]		public string ConnectionId { get; set; }		[DisplayName("用户ID")]		public int UserID { get; set; }		[DisplayName("用户名")]		public string UserName { get; set; }		[DisplayName("用户类型")]		public int TypeID { get; set; }		[DisplayName("连入时间")]		public DateTime ConnectionTime { get; set; }		public HubUser(string connID,int userID, string name,int typeID)		{			ConnectionId = connID;			UserID = userID;			UserName = name;			TypeID = typeID;			ConnectionTime = DateTime.Now;		}	}	public class WebMessage	{		public string ToConnID{get;set;}		public DateTime MessageDate{get;set;}		public string MessageContent { get; set; }		public bool IsAnswer{get;set;}		public int RepeatCounts { get; set; }		public bool IsRemovable { get; set; }		public WebMessage()		{			ToConnID=string.Empty;			MessageDate=DateTime.Now;			MessageContent = string.Empty;			IsAnswer=false;			RepeatCounts = 0;			IsRemovable = false;		}	}}

 最后，在Activity中增加对FireHub的使用，参考代码如下：

public class SignalRActivity : Activity	{		private FireHub _fireHub = null;                private UsersEntity _user = null;		                protected override void OnCreate (Bundle bundle)		{			base.OnCreate (bundle);			// Create your application here			SetContentView(Resource.Layout.SignalR);			_user = new UsersEntity ();			Button btnConnectHub = FindViewById (Resource.Id.btnConnectHub);			btnConnectHub.Text = "监控网站连接";			btnConnectHub.Click += btnConnectHubClick;		}		protected void btnConnectHubClick(object sender,EventArgs e)		{			try			{				if (_fireHub != null)				{					StopHub();					lock (_syncUser)					{						_hubUser.Clear();					}					//UpdateList();				}				else				{					if (HubReconnect(false))					{						RunOnUiThread(new Action(()=>{ _txtView.Text=string.Format("{0}: 实时网站连接成功", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));}));					}					else					{						RunOnUiThread(new Action(()=>{ _txtView.Text=string.Format("{0}: 实时网站连接失败", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));}));											}				}			}			catch (Exception err)			{				//FormMain.STAErrLogger.Write(string.Format("{0}({1}-{2})", err.Message, "FormMain", "btnConnectHub_Click"));			}		}		#region HUB管理		bool HubReconnect(bool checkNull=true)		{			bool bRet = false;			bool isUpdate = false;			//重新连接到服务网站			if (!checkNull || _fireHub != null)			{				if (_fireHub != null)					_fireHub.IsConnected = false;				if (!ConnectHubServer())				{				}				else				{					bRet = true;				}				isUpdate = true;			}			return bRet;		}		public bool ConnectHubServer()		{			try			{				if (_fireHub == null)					_fireHub = new FireHub();				else				{					if (_fireHub.IsConnected)						return true;				}				if (!_fireHub.Connect("http://your service web", 5000))				{					RunOnUiThread(new Action(()=>{ _txtView.Text="实时报警服务网站不在服务状态";}));					if (_fireHub != null)					{						string strDispose = _fireHub.Dispose();						if (!string.IsNullOrEmpty(strDispose))						{							//FormMain.STAErrLogger.Write(string.Format("{0}({1})", "ConnectHubServer-0", strDispose));						}					}					_fireHub = null;					return false;				}				else				{										if (_fireHub.ConnectToServer(_user))					{						_fireHub.Receive -= _fireHub_Receive;						_fireHub.Receive += _fireHub_Receive;						_fireHub.CloseHub -= _fireHub_CloseHub;						_fireHub.CloseHub += _fireHub_CloseHub;						_fireHub.StateChanged -= _fireHub_StateChanged;						_fireHub.StateChanged += _fireHub_StateChanged;						_fireHub.AddWebMessage -= _fireHub_AddWebMessage;						_fireHub.AddWebMessage += _fireHub_AddWebMessage;						if (_webMessageManage == null)						{							_webMessageManage = new WebMessageManage();							_webMessageManage.WebMessageCallback += _webMessageManage_WebMessageCallback;						}						RunOnUiThread(new Action(()=>{ _txtView.Text="成功连接到实时报警服务网站";}));					}					else					{						RunOnUiThread(new Action(()=>{ _txtView.Text="连接到实时报警服务网站失败，请重新尝试";}));						string strDispose = _fireHub.Dispose();						if(!string.IsNullOrEmpty(strDispose))						{						}						_fireHub = null;						return false;					}				}				return true;			}			catch (Exception err)			{				return false;			}		}		#endregion		#region FireHub事件实现		void _fireHub_Receive(string msg)		{			try			{				HubMessage hm = new HubMessage();				hm = Newtonsoft.Json.JsonConvert.DeserializeObject
      
       (msg);				if (hm == null)					return;				if (hm.M == "onConnected")				{					#region 客户端连接成功后的反馈消息					#endregion				}				else if (hm.M == "onNewUserConnected")				{					#region 有新的客户端接入					#endregion				}				else if (hm.M == "onUserDisconnected")				{					#region 客户端断开					#endregion				}				else if (hm.M == "messageReceived")				{					#region 定时广播巡查					#endregion				}				else if (hm.M == "sendCallbackMessage")				{					#region 私人消息发出成功后，返回反馈消息					#endregion				}				else if (hm.M == "sendPrivateMessage")				{					#region 接收到私人消息					#endregion				}			}			catch (Exception err)			{				RunOnUiThread(new Action(()=>{					_txtView.Text="HUB Error:" + err.Message + err.Source;				}));			}		}		void _fireHub_CloseHub()		{			StopHub();		}		public void StopHub()		{			try			{				RunOnUiThread(new Action(()=>{					_txtView.Text="实时报警服务网站关闭";				}));				if (_fireHub == null)					return;				string strDispose = _fireHub.Dispose();				if (!string.IsNullOrEmpty(strDispose))				{				}				_fireHub = null;				RunOnUiThread(new Action(()=>{					ChangeHubButtonStatus();				}));			}			catch (Exception err)			{			}		}		void _webMessageManage_WebMessageCallback(int flag)		{			try			{				if (flag == 0)				{					if ((DateTime.Now - _dtHubReconnect).TotalMinutes < 30)					{						return;					}					RunOnUiThread(new Action(()=>{					}));					//重新连接到服务网站					if(HubReconnect(true))					{						_dtHubReconnect = DateTime.Now;					}				}			}			catch (Exception err)			{			}		}		void _fireHub_AddWebMessage(WebMessage wm)		{			try			{				if (_webMessageManage != null)				{					_webMessageManage.AddMessage(wm);				}			}			catch (Exception err)			{			}		}		void _fireHub_StateChanged(int state, string msg)		{			try			{				switch (state)				{				case 0://断开连接了					{						RunOnUiThread(new Action(()=>{							_txtView.Text="HUB掉线";						}));							StopHub();					}					break;				case 1://HUB异常					{						RunOnUiThread(new Action(()=>{							_txtView.Text=msg;						}));								StopHub();					}					break;				}			}			catch (Exception err)			{			}		}		#endregion    }
      

      完成以后编译通过，并且能够实现服务器和客户端的实时消息推送。