diff --git a/HW-Async&Thread-1/Program.cs b/HW-Async&Thread-1/Program.cs
index 6965f01..70850e4 100644
--- a/HW-Async&Thread-1/Program.cs
+++ b/HW-Async&Thread-1/Program.cs
@@ -56,12 +56,13 @@ public abstract class Expr
 public class ValueExpr(int initVal) : Expr
 {
     int val = initVal;
+    readonly object valLock = new();
     public override int Val
     {
         get
         {
-            // TODO 1:读取操作
-            return val;
+            lock (valLock)
+                return val;
         }
     }
 
@@ -74,16 +75,23 @@ public int NewVal
         set
         {
             // TODO 2:修改操作
+            lock (valLock)
+                val = value;
+            Update().Wait();
         }
     }
 
     public override async Task Update()
     {
         // TODO 3:更新操作
+         if (parent != null)
+             await parent.Update();
     }
 
     public override void Register(Expr parent)
     {
+        this.parent = parent;
+        Update().Wait();
         // TODO 4:注册操作
     }
 }
@@ -95,12 +103,14 @@ public override void Register(Expr parent)
 public class AddExpr : Expr
 {
     int val = 0;
+    readonly object valLock = new();
     public override int Val
     {
         get
         {
             // TODO 5:读取操作
-            return val;
+             lock (valLock)
+                 return val;
         }
     }
 
@@ -116,10 +126,16 @@ public AddExpr(Expr A, Expr B)
     public override async Task Update()
     {
         // TODO 6:更新操作
+        lock (valLock)
+            val = ExprA.Val + ExprB.Val;
+        if (parent != null)
+            await parent.Update();
     }
 
     public override void Register(Expr parent)
     {
         // TODO 7:注册操作
+        this.parent = parent;
+        Update().Wait();
     }
 }