diff --git a/Tiobon.Core.Services/Ghre/Ghre_ExamPaperServices.cs b/Tiobon.Core.Services/Ghre/Ghre_ExamPaperServices.cs
index 8b95a4dc..951b8c19 100644
--- a/Tiobon.Core.Services/Ghre/Ghre_ExamPaperServices.cs
+++ b/Tiobon.Core.Services/Ghre/Ghre_ExamPaperServices.cs
@@ -943,6 +943,9 @@ delete from Ghre_ExamPaperQuestion WHERE ExamPaperId='{id}';");
     {
 
         var entity = await base.QueryById(id);
+        if(entity is null )
+            return ServiceResult.OprateFailed("无效的ID！");
+
         entity.PaperName = entity.PaperName + "_复制";
         entity.PaperNo = await GenerateContinuousSequence("Ghre_ExamPaper", "PaperNo", "P");