C#通过KEPServer对PLC进行读写（二）：读取

在通过OPCAutomation我们先了解下这个类下的三个对象

1.OPCServer：创建OPC的连接

2.OPCBrowser：创建OPC浏览对象

3.OPCGroups：OPC通信组对象

4.OPCItem：单个代操作（读取的对象）

具体的读取流程如下：

1.获取当前程序下的所有IP地址/计算机名，将得到的对象存入控件

 IPHostEntry  IPHost = Dns.GetHostEntry(Environment.MachineName);
            if (IPHost.AddressList.Length>0)
            {
                for (int i = 0; i < IPHost.AddressList.Length; i++)
                {
                    string host = Dns.GetHostEntry(IPHost.AddressList[i].ToString()).HostName;

                    if (!this.cmb_ServerNode.Items.Contains(host))
                    {
                        this.cmb_ServerNode.Items.Add(host);
                    }
                }
            }                     

2.根据选择的IP地址/计算机名得到OPC服务名称列表，并加载进控件

 KepSever = new OPCServer();
            object serverList = KepSever.GetOPCServers(this.cmb_ServerNode.Text);

            foreach (var item in (Array) serverList)
            {
                if (!this.cmb_ServerName.Items.Contains(item) )
                {
                    this.cmb_ServerName.Items.Add(item);
                } 
            }

3.连接OPC服务器，其中KepBrowser记录的就是服务器内所有的标签变量，接下来就是创建组并激活，开启订阅功能，并且绑定读的操作

 //建立连接 
                if (KepSever == null)
                {
                   KepSever = new OPCServer(); 
                }

                try
                {
                    KepSever.Connect(this.cmb_ServerName.Text, this.cmb_ServerNode.Text);
                }
                catch (Exception ex)
                {

                    MessageBox.Show("连接失败：" + ex.Message);
                    return;
                }
                this.btn_Connect.Text = "disConn";

                //获取OPC所有的变量
                KepBrowser = KepSever.CreateBrowser();
                KepBrowser.ShowBranches();
                KepBrowser.ShowLeafs(true);

                this.lst_Items.Items.Clear();
                foreach (var item in KepBrowser)
                {
                    this.lst_Items.Items.Add(item);   //将获取到的变量标签存入控件
                }

                //初始化OPCGroup
                KepGroups = KepSever.OPCGroups;
                KepGroups.DefaultGroupDeadband = 0;   //死区值，设为0时，服务器端该组内任何数据变化都通知组
                KepGroups.DefaultGroupIsActive = true;   

                KepGroup = KepGroups.Add("测试通讯组");
                KepGroup.IsActive = true;    //激活组
                KepGroup.IsSubscribed = true;   //开启订阅功能
                KepGroup.UpdateRate = 250;

                //增加一个事件
                KepGroup.AsyncReadComplete +=KepGroup_AsyncReadComplete;

4.添加需要读取的标签到列表中

 this.OPCList.Add(new OPCItem()
                {
                    ItemID = this.lst_Items.SelectedItem.ToString()
                });

                int count = this.OPCList.Count;
                List<string> ItemIDs = new List<string>();
                List<int> ClientHandles  = new List<int>();
                ItemIDs.Add("0");
                ClientHandles.Add(0);

                for (int i = 0; i < count; i++)
            {
                ItemIDs.Add(this.OPCList[i].ItemID);
                ClientHandles.Add(i);
             
            }
                //集合转换成array
                Array ItemID = ItemIDs.ToArray();
                Array ClientHandle = ClientHandles.ToArray();


                KepGroup.OPCItems.AddItems(count, ref ItemID, ref ClientHandle, out SeverHandles, out Errors);

5.开启定时器，定时读取

        private void timer1_Tick(object sender, EventArgs e)
        {
            if (KepSever != null)
            {
                if (this.OPCList.Count>0)
                {
                    KepGroup.AsyncRead(this.OPCList.Count, ref SeverHandles, out Errors, TransactionID, out CancelID);
                }
            }
        }

6.读取数据并解析

        private void KepGroup_AsyncReadComplete(int TransactionID, int NumItems, ref Array ClientHandles, ref Array ItemValues, ref Array Qualities, ref Array TimeStamps, ref Array Errors)
        {
            //解析数据
           
            for (int i = 1; i <= NumItems; i++)
            {
                object value = ItemValues.GetValue(i);
                if (value != null)
                {
                   int  ClientHandle=Convert.ToInt32(ClientHandles.GetValue(i));
                   for (int j = 0; j < this.OPCList.Count; j++)
                   {
                       if (j == ClientHandle)
                       {
                           this.OPCList[j].Value = value.ToString();
                           this.OPCList[j].UpdateTime = TimeStamps.GetValue(i).ToString();
                           this.OPCList[j].Quanlity = Qualities.GetValue(i).ToString();

                       }
                   }
                }
            }

            this.dataGridView1.DataSource = null;
            this.dataGridView1.DataSource = this.OPCList;

        }

 参考文档：https://blog.csdn.net/guorui_java/article/details/104247734