zhanghongzhi1234_EMS/OpcLibrary/ConnectionPoint.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using OpcRcw.Comn;

namespace OpcLibrary
{
    /// <summary>
    /// Adds and removes a connection point to a server.
    /// </summary>
    public class ConnectionPoint : IDisposable
    {
        /// <summary>
        /// The COM server that supports connection points.
        /// </summary>
        private IConnectionPoint m_server = null;

        /// <summary>
        /// The id assigned to the connection by the COM server.
        /// </summary>
        private int m_cookie = 0;

        /// <summary>
        /// The number of times Advise() has been called without a matching Unadvise(). 
        /// </summary>
        private int m_refs = 0;

        /// <summary>
        /// Initializes the object by finding the specified connection point.
        /// </summary>
        public ConnectionPoint(object server, Guid iid)
        {
            ((IConnectionPointContainer)server).FindConnectionPoint(ref iid, out m_server);
        }

        /// <summary>
        /// Releases the COM server.
        /// </summary>
        public void Dispose()
        {
            if (m_server != null)
            {
                while (Unadvise() > 0) ;
                OpcLibrary.Com.Interop.ReleaseServer(m_server);
                m_server = null;
            }
        }

        /// <summary> 
        /// The cookie returned in the advise call. 
        /// </summary> 
        public int Cookie
        {
            get { return m_cookie; }
        }

        //=====================================================================
        // IConnectionPoint

        /// <summary>
        /// Establishes a connection, if necessary and increments the reference count.
        /// </summary>
        public int Advise(object callback)
        {
            if (m_refs++ == 0) m_server.Advise(callback, out m_cookie);
            return m_refs;
        }

        /// <summary>
        /// Decrements the reference count and closes the connection if no more references.
        /// </summary>
        public int Unadvise()
        {
            if (--m_refs == 0) m_server.Unadvise(m_cookie);
            return m_refs;
        }
    }
}
