diff --git "a/07_\351\207\207\346\240\267\346\240\207\346\263\250/07_\351\207\207\346\240\267\346\240\207\346\263\250/Class1.cs" "b/07_\351\207\207\346\240\267\346\240\207\346\263\250/07_\351\207\207\346\240\267\346\240\207\346\263\250/Class1.cs"
index 6b1177b66bad31999bff1e81488596f535455b98..c0f09a167e79417742cb7e92b73237da074f6c22 100644
--- "a/07_\351\207\207\346\240\267\346\240\207\346\263\250/07_\351\207\207\346\240\267\346\240\207\346\263\250/Class1.cs"
+++ "b/07_\351\207\207\346\240\267\346\240\207\346\263\250/07_\351\207\207\346\240\267\346\240\207\346\263\250/Class1.cs"
@@ -1,4 +1,4 @@
-using Autodesk.AutoCAD.ApplicationServices;
+using Autodesk.AutoCAD.ApplicationServices;
 using Autodesk.AutoCAD.DatabaseServices;
 using Autodesk.AutoCAD.EditorInput;
 using Autodesk.AutoCAD.Geometry;
@@ -22,10 +22,10 @@ namespace _07_采样标注
             Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
             // 提示用户选择基准线和采样线
             PromptEntityResult perBase = ed.GetEntity("\n 请选择基准线：");
-            if (perBase.Status != PromptStatus.OK) return; // 如果没有选择
+            if (perBase.Status != PromptStatus.OK || perBase.ObjectId==ObjectId.Null) return; // 如果没有选择
             ObjectId baseEntityId = perBase.ObjectId;
             PromptEntityResult perCurve = ed.GetEntity("\n 请选择采样线：");
-            if (perCurve.Status != PromptStatus.OK) return;
+            if (perCurve.Status != PromptStatus.OK || perCurve.ObjectId==ObjectId.Null) return;
             // 获取基准线和采样线图形实体对象
             Entity baseEntity = this.GetEntity(db, perBase.ObjectId);
             Entity curve = this.GetEntity(db, perCurve.ObjectId);