diff --git a/AppLibs/AppLibs/Libs/NavItem.cs b/AppLibs/AppLibs/Libs/NavItem.cs
index 393b2f1..ed337c3 100644
--- a/AppLibs/AppLibs/Libs/NavItem.cs
+++ b/AppLibs/AppLibs/Libs/NavItem.cs
@@ -1,4 +1,6 @@
-using Newtonsoft.Json;
+using Microsoft.AspNetCore.Html;
+using Microsoft.Extensions.Logging.Console;
+using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -23,8 +25,9 @@ namespace AppLibs.Libs
 
         [JsonProperty(PropertyName = "url")]
         public string Url { set; get; }
-        [JsonProperty(PropertyName = "flexPage")]
-        public bool IsFlexPage { set; get; }
+
+        [JsonProperty(PropertyName = "flexpage")]
+        public bool? IsFlexPage { set; get; }
 
         [JsonProperty(PropertyName = "sub-item")]
         public List<NavItem> SubItem { set; get; }
@@ -40,5 +43,19 @@ namespace AppLibs.Libs
             SubItem = new List<NavItem>();
         }
 
+        public IHtmlContent ToFlexPageAttribute()
+        {
+            Console.WriteLine(IsFlexPage.ToString());
+            if (IsFlexPage.HasValue && IsFlexPage.Value)
+            {
+                
+                return new HtmlString("IsFlexPage");
+            }
+            else
+            {
+                return new HtmlString("");
+            }
+        }
+
     }
 }
diff --git a/AppLibs/AppLibs/Libs/WSNavigation.cs b/AppLibs/AppLibs/Libs/WSNavigation.cs
index 425f878..096bb72 100644
--- a/AppLibs/AppLibs/Libs/WSNavigation.cs
+++ b/AppLibs/AppLibs/Libs/WSNavigation.cs
@@ -9,40 +9,47 @@ namespace AppLibs.Libs
 {
     public class WSNavigation
     {
-        private static List<NavItem> list;
+        private static List<NavItem> list = new List<NavItem>() ;
+        private static readonly object loadLock = new object();
+        private static Task? t;
 
-        private static Task t;
-
-        public static void LoadJson()
+        public static async Task LoadJson()
         {
-            t = Task.Run(() => LoadNavItem());
+            lock (loadLock)
+            {
+                // Nếu đang có task load cũ chưa xong, có thể đợi hoặc hủy (tùy logic)
+                if (t != null && !t.IsCompleted)
+                    return;
+
+                t = LoadNavItem();
+            }
+            await t.ConfigureAwait(false);
         }
 
         static async Task LoadNavItem()
         {
-            list = new List<NavItem>();
+            var newList = new List<NavItem>();
             using (var reader = new StreamReader(Path.GetFullPath("Json/navlist.json")))
             {
-                string json = await reader.ReadToEndAsync();
-                list = JsonConvert.DeserializeObject<List<NavItem>>(json);
+                string json = await reader.ReadToEndAsync().ConfigureAwait(false);
+                var deserializedList = JsonConvert.DeserializeObject<List<NavItem>>(json);
+                if (deserializedList != null)
+                {
+                    newList = deserializedList;
+                }
             }
+            System.Threading.Interlocked.Exchange(ref list, newList);
         }
-        public static List<NavItem> GetListMenu()
+        public static async Task<List<NavItem>> GetListMenu()
         {
             if (t != null)
             {
-                if (t.IsCompleted)
+                if (!t.IsCompleted)
                 {
-                    return list;
-                }
-                else
-                {
-                    t.Wait();
-                }
-                return list;
+                    await t;
+                } 
             }
-            return new List<NavItem>();
-
+            return list;
         }
     }
 }
diff --git a/ManagementApp/Program.cs b/ManagementApp/Program.cs
index 0767499..94ffb00 100644
--- a/ManagementApp/Program.cs
+++ b/ManagementApp/Program.cs
@@ -3,7 +3,7 @@ using AppLibs.Libs;
 using ManagementApp.Models.Services;
 using Microsoft.AspNetCore.Server.Kestrel.Core;
 
-WSNavigation.LoadJson();
+await WSNavigation.LoadJson().ConfigureAwait(false);
 
 var builder = WebApplication.CreateBuilder(args);