Optimize code and remove Action

https://github.com/2dust/v2rayN/issues/6638

v2rayN/ServiceLib/Handler/ConfigHandler.cs

@@ -105,14 +105,9 @@ namespace ServiceLib.Handler
 
             if (Utils.IsNullOrEmpty(config.UiItem.CurrentLanguage))
             {
-                if (Thread.CurrentThread.CurrentCulture.Name.Equals("zh-cn", StringComparison.CurrentCultureIgnoreCase))
-                {
-                    config.UiItem.CurrentLanguage = Global.Languages.First();
-                }
-                else
-                {
-                    config.UiItem.CurrentLanguage = Global.Languages[2];
-                }
+                config.UiItem.CurrentLanguage = Thread.CurrentThread.CurrentCulture.TwoLetterISOLanguageName.Equals("zh", StringComparison.CurrentCultureIgnoreCase)
+                    ? Global.Languages.First()
+                    : Global.Languages[2];
             }
 
             config.ConstItem ??= new ConstItem();

v2rayN/ServiceLib/Services/UpdateService.cs

@@ -243,7 +243,7 @@ namespace ServiceLib.Services
             _updateFunc?.Invoke(true, string.Format(ResUI.MsgDownloadGeoFileSuccessfully, "geo"));
         }
 
-        public async Task RunAvailabilityCheck(Action<bool, string> updateFunc)
+        public async Task<string> RunAvailabilityCheck()
         {
             var downloadHandle = new DownloadService();
             var time = await downloadHandle.RunAvailabilityCheck(null);
@@ -255,7 +255,7 @@ namespace ServiceLib.Services
                 ip = $"({ipInfo?.country_code}) {ipInfo?.ip}";
             }
 
-            updateFunc?.Invoke(false, string.Format(ResUI.TestMeOutput, time, ip));
+            return string.Format(ResUI.TestMeOutput, time, ip);
         }
 
         #region CheckUpdate private

v2rayN/ServiceLib/ViewModels/StatusBarViewModel.cs

@@ -311,11 +311,11 @@ namespace ServiceLib.ViewModels
             {
                 return;
             }
-            await (new UpdateService()).RunAvailabilityCheck(async (bool success, string msg) =>
-            {
-                NoticeHandler.Instance.SendMessageEx(msg);
-                _updateView?.Invoke(EViewAction.DispatcherServerAvailability, msg);
-            });
+
+            var msg = await (new UpdateService()).RunAvailabilityCheck();
+
+            NoticeHandler.Instance.SendMessageEx(msg);
+            _updateView?.Invoke(EViewAction.DispatcherServerAvailability, msg);
         }
 
         public void TestServerAvailabilityResult(string msg)