diff --git a/BlazorApp/BlazorApp/Pages/Counter.razor b/BlazorApp/BlazorApp/Pages/Counter.razor
index ef23cb3..f9602b1 100644
--- a/BlazorApp/BlazorApp/Pages/Counter.razor
+++ b/BlazorApp/BlazorApp/Pages/Counter.razor
@@ -7,6 +7,7 @@
 <p role="status">Current count: @currentCount</p>
 
 <button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
+<button class="btn btn-secondary" @onclick="AutoIncrement">Auto Increment</button>
 
 @code {
     private int currentCount = 0;
@@ -15,4 +16,16 @@
     {
         currentCount++;
     }
+
+    private void AutoIncrement()
+    {
+        Timer timer = new Timer(x =>
+        {
+            InvokeAsync(() =>
+            {
+                IncrementCount();
+                StateHasChanged();
+            });
+        }, null, 1000, 1000);
+    }
 }
diff --git a/BlazorApp/BlazorApp/Pages/User.razor b/BlazorApp/BlazorApp/Pages/User.razor
index a666fab..5a87991 100644
--- a/BlazorApp/BlazorApp/Pages/User.razor
+++ b/BlazorApp/BlazorApp/Pages/User.razor
@@ -28,7 +28,9 @@
             <input class="form-control" placeholder="Add User" @bind-value="_inputName"/>
         </div>
         <div class="col">
-            <button class="btn btn-primary" type="button" @onclick="AddUser">Add a user</button>
+            @* 속성(Attribute)도 binding 가능 *@
+            @* conditional atribute 속성 자체에도 조건 붙일 수 있음 *@
+            <button class=@_btnClass type="button" @onclick="AddUser" disabled="@(_users.Count >= 5)">Add a user</button>
         </div>
     </div>
 </div>
@@ -37,12 +39,15 @@
     private List<UserData> _users = new List<UserData>();
 
     private string _inputName;
+    private string _btnClass = "btn btn-primary";
 
     protected override void OnInitialized()
     {
         _users.Add(new UserData() { Name = "Simpson" });
         _users.Add(new UserData() { Name = "Richard" });
         _users.Add(new UserData() { Name = "Tylor" });
+
+        RefreshButton();
     }
 
     private void AddUser()
@@ -52,10 +57,22 @@
 
         _users.Add(new UserData() { Name = _inputName });
         _inputName = "";
+
+        RefreshButton();
     }
 
     private void KickUser(UserData user)
     {
         _users.Remove(user);
+
+        RefreshButton();
+    }
+
+    private void RefreshButton()
+    {
+        if (_users.Count % 2 == 0)
+            _btnClass = "btn btn-primary";
+        else
+            _btnClass = "btn btn-secondary";
     }
 }