快速检测数据库是否连接上（与其它主机连接）

在连接主机数据库的时候如果连接不上，会等待很长时间。其实并不是连接数据库慢，而是连接到数据库所在的主机慢。

using System;
 using System.Collections.Generic;
 using System.Linq;
using System.Text;

using System.Net.Sockets;
using System.Threading;

namespace Commone
{
    /// <summary>
    /// 网络端口状态检查类 
    /// </summary>
    public class NetPortOp
    {
        private static bool IsConnectionSuccessful = false;
        private static Exception socketexception;
        private static ManualResetEvent TimeoutObject = new ManualResetEvent(false);

        /// <summary>
        /// 验证连接指定主机的端口
        /// </summary>
        /// <param name="host">主机IP或名称</param>
        /// <param name="port">端口号</param>
        /// <param name="timeoutMSec">超时时长(毫秒)</param>
        /// <returns>bool</returns>
        public static bool ConnValidate(string host, int port, int timeoutMSec)
        {
            bool ret = false;

            TimeoutObject.Reset();
            socketexception = null;

            TcpClient tcpclient = new TcpClient();

            tcpclient.BeginConnect(host, port, new AsyncCallback(CallBackMethod), tcpclient);
            if (TimeoutObject.WaitOne(timeoutMSec, false))
            {
                if (IsConnectionSuccessful)
                {
                    ret = true;
                    tcpclient.Client.Close();
                }
                else
                {
                    //不用抛出异常，根据ret判断连接成功与否
                    //throw socketexception;
                }
            }
            else
            {
                //不用抛出异常，根据ret判断连接成功与否
                //throw new TimeoutException("TimeOut Exception");
            }

            tcpclient.Close();
            return ret;
        }

        private static void CallBackMethod(IAsyncResult asyncresult)
        {
            try
            {
                IsConnectionSuccessful = false;
                TcpClient tcpclient = asyncresult.AsyncState as TcpClient;

                if (tcpclient.Client != null)
                {
                    tcpclient.EndConnect(asyncresult);
                    IsConnectionSuccessful = true;
                }
            }
            catch (Exception ex)
            {
                IsConnectionSuccessful = false;
                socketexception = ex;
            }
            finally
            {
                TimeoutObject.Set();
            }
        }
    }
}

bool b = Commone.NetPortOp.ConnValidate("192.168.1.119", 1433, 1000);
//连接上返回true，否则返回false。