diff --git a/Modbus.Net/Modbus.Net/Controller/DuplicateWithCount.cs b/Modbus.Net/Modbus.Net/Controller/DuplicateWithCount.cs
index f68f757..8050aa3 100644
--- a/Modbus.Net/Modbus.Net/Controller/DuplicateWithCount.cs
+++ b/Modbus.Net/Modbus.Net/Controller/DuplicateWithCount.cs
@@ -13,8 +13,7 @@ namespace Modbus.Net
         /// </summary>
         /// <param name="receiveMessage">收到的报文信息</param>
         /// <param name="packageCountPositions">收到的断包长度查询位置</param>
-        /// <param name="otherCount">除掉长度查询信息外其它报文的长度
-        ///                          注意：该长度不包含CRC校验</param>
+        /// <param name="otherCount">除掉长度查询信息外其它报文的长度</param>
         /// <returns>切分后的报文信息</returns>
         private static ICollection<byte[]> DuplicateMessages(byte[] receiveMessage, ICollection<int> packageCountPositions, int otherCount)
         {
@@ -51,8 +50,7 @@ namespace Modbus.Net
         ///     获取按照长度断包的函数
         /// </summary>
         /// <param name="packageCountPositions">断包长度的位置信息</param>
-        /// <param name="otherCount">除掉长度查询信息外其它报文的长度
-        ///                          注意：该长度不包含CRC校验</param>
+        /// <param name="otherCount">除掉长度查询信息外其它报文的长度</param>
         /// <returns>断包函数</returns>
         public static Func<byte[], ICollection<byte[]>> GetDuplcateFunc(ICollection<int> packageCountPositions, int otherCount)
         {
diff --git a/Modbus.Net/Modbus.Net/Job/MachineJobScheduler.cs b/Modbus.Net/Modbus.Net/Job/MachineJobScheduler.cs
index 52e7653..67a35cf 100644
--- a/Modbus.Net/Modbus.Net/Job/MachineJobScheduler.cs
+++ b/Modbus.Net/Modbus.Net/Job/MachineJobScheduler.cs
@@ -94,8 +94,12 @@ namespace Modbus.Net
 
         public async Task<MachineSetJobScheduler> Query(string queryId = null, Func<Dictionary<string, ReturnUnit>, Dictionary<string, ReturnUnit>> QueryDataFunc = null)
         {
-            JobChainingJobListenerWithDataMap listener = _scheduler.ListenerManager.GetJobListener("Modbus.Net.DataQuery.Chain") as JobChainingJobListenerWithDataMap;
-            if (listener == null)
+            JobChainingJobListenerWithDataMap listener;
+            try
+            {
+                listener = _scheduler.ListenerManager.GetJobListener("Modbus.Net.DataQuery.Chain") as JobChainingJobListenerWithDataMap;
+            }
+            catch
             {
                 listener = new JobChainingJobListenerWithDataMap("Modbus.Net.DataQuery.Chain", false);
                 _scheduler.ListenerManager.AddJobListener(listener, GroupMatcher<JobKey>.GroupEquals("Modbus.Net.DataQuery.Group"));