update panasonic driver

SCADA/Program/PanasonicDriver/PanasonicSerialReader.cs

@@ -5,7 +5,6 @@ using System.ComponentModel;
 using System.Globalization;
 using System.IO;
 using System.IO.Ports;
-using System.Net;
 using System.Text;
 
 namespace PanasonicPLCriver
@@ -340,7 +339,8 @@ namespace PanasonicPLCriver
             }
             catch (Exception e)
             {
-                OnClose?.Invoke(this, new ShutdownRequestEventArgs(e.Message));
+                if (OnClose != null)
+                    OnClose(this, new ShutdownRequestEventArgs(e.Message));
                 return null;
             }
         }
@@ -359,14 +359,16 @@ namespace PanasonicPLCriver
                 }
                 catch (Exception)
                 {
-                    OnClose?.Invoke(this, new ShutdownRequestEventArgs("读取超时"));
+                    if (OnClose != null)
+                        OnClose(this, new ShutdownRequestEventArgs("读取超时"));
                     return null;
                 }
             }
             if (recv.Substring(3, 1) == "!")//返回为错误代码
             {
                 string err = recv.Substring(4, 2);
-                OnClose?.Invoke(this, new ShutdownRequestEventArgs(daveStrerror(err)));
+                if (OnClose != null)
+                    OnClose(this, new ShutdownRequestEventArgs(daveStrerror(err)));
                 return null;
             }
             string needXorStr = recv.Substring(0, recv.Length - 2);//需要进行xor校验的字符串
@@ -374,7 +376,8 @@ namespace PanasonicPLCriver
             string checkStr = Utility.XorCheck(needXorStr);
             if (checkStr != recvCheck)
             {
-                OnClose?.Invoke(this, new ShutdownRequestEventArgs("校验失败"));
+                if (OnClose != null)
+                    OnClose(this, new ShutdownRequestEventArgs("校验失败"));
                 return null;
             }
             else