diff --git a/YD_AllHeartRates.Api/Mqtt/MqttBackgroundService.cs b/YD_AllHeartRates.Api/Mqtt/MqttBackgroundService.cs
index c8233b2..39b4c02 100644
--- a/YD_AllHeartRates.Api/Mqtt/MqttBackgroundService.cs
+++ b/YD_AllHeartRates.Api/Mqtt/MqttBackgroundService.cs
@@ -97,25 +97,29 @@ namespace YD_AllHeartRates.Api.Mqtt
 
                 if (studentList == null || devices == null)
                 {
-                    studentList = (from d in _smartSportsContext.Device
-                                   join s in _smartSportsContext.Student on d.StudentNo equals s.StudentNo
-                                   join c in _smartSportsContext.Class on s.ClassId equals c.Id
-                                   where s.SchoolCode == AppSettings.SchoolCode && s.StudentStatus == 1
-                                   select new StudentDto
-                                   {
-                                       SchoolCode = s.SchoolCode,
-                                       StudentNo = s.StudentNo,
-                                       StudentName = s.StudentName,
-                                       Sex = s.Sex,
-                                       Age = s.Age,
-                                       HeartRateId = d.Code,
-                                       JumpRopeId = d.Code,
-                                       ClassId = s.ClassId,
-                                       ClassName = s.ClassName,
-                                       GradeId = c.GradeId,
-                                       GradeName = c.GradeName ?? "",
-                                       DeviceType = d.DeviceType,
-                                   }).ToList();
+                    studentList = (
+                       from s in _smartSportsContext.Student
+                       join c in _smartSportsContext.Class on s.ClassId equals c.Id
+                       join d in _smartSportsContext.Device on s.StudentNo equals d.StudentNo into sd
+                       from d in sd.DefaultIfEmpty()
+                       where s.SchoolCode == AppSettings.SchoolCode && s.StudentStatus == 1
+                       select new StudentDto
+                       {
+                           SchoolCode = s.SchoolCode,
+                           StudentNo = s.StudentNo,
+                           StudentName = s.StudentName,
+                           Sex = s.Sex,
+                           Age = s.Age,
+                           HeartRateId = d != null ? d.Code : "",
+                           JumpRopeId = d != null ? d.Code : "",
+                           ClassId = s.ClassId,
+                           ClassName = s.ClassName,
+                           GradeId = c.GradeId,
+                           GradeName = c.GradeName ?? "",
+                           DeviceType = d != null ? d.DeviceType : 0
+                       }
+                   ).ToList();
+
 
                     devices = _smartSportsContext.Device.Where(x => x.SchoolCode == AppSettings.SchoolCode && !string.IsNullOrWhiteSpace(x.StudentNo)).ToList();
 
diff --git a/YD_AllHeartRates.Api/XS.cs b/YD_AllHeartRates.Api/XS.cs
deleted file mode 100644
index 2f067d2..0000000
--- a/YD_AllHeartRates.Api/XS.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-namespace YD_AllHeartRates.Api
-{
-    public class XS
-    {
-        /*
-        「」
-        为了确定魏恒是否喝了酒，
-        我去电话亭给他打了一个电话，
-        我故意用言语激怒他，听到杯子摔碎得声音，
-        我知道我的计划成功了。
-        随后便是魏恒倒下得声音。
-
- 
-        
-
-
-
-
-
-
-        */
-    }
-}
diff --git a/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfo.cs b/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfo.cs
index 918077b..5236787 100644
--- a/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfo.cs
+++ b/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfo.cs
@@ -14,7 +14,7 @@ using System.Reflection;
 [assembly: System.Reflection.AssemblyCompanyAttribute("YD_AllHeartRates.Api")]
 [assembly: System.Reflection.AssemblyConfigurationAttribute("Debug")]
 [assembly: System.Reflection.AssemblyFileVersionAttribute("1.0.0.0")]
-[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+adb7a5132ba408ee1c99d16fb2ead9bed7a7ccc5")]
+[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+4af2ed6c7dde8915d38199959dc15eb0626ad29e")]
 [assembly: System.Reflection.AssemblyProductAttribute("YD_AllHeartRates.Api")]
 [assembly: System.Reflection.AssemblyTitleAttribute("YD_AllHeartRates.Api")]
 [assembly: System.Reflection.AssemblyVersionAttribute("1.0.0.0")]
diff --git a/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfoInputs.cache b/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfoInputs.cache
index 7653a50..2618ff6 100644
--- a/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfoInputs.cache
+++ b/YD_AllHeartRates.Api/obj/Debug/net6.0/YD_AllHeartRates.Api.AssemblyInfoInputs.cache
@@ -1 +1 @@
-6198966bba43cd9c423a58fba5f3c39b124d08b73c11ccc008ce22ad17ebb10f
+beaa3e786d777e801e865749bc1ed887c9c8bed6062702fc86efc5e999ecbaef