diff --git a/Engine/Attributes/LCEngineClassHookAttribute.cs b/Engine/Attributes/LCEngineClassHookAttribute.cs
index a3e0a5d..6fbe6d8 100644
--- a/Engine/Attributes/LCEngineClassHookAttribute.cs
+++ b/Engine/Attributes/LCEngineClassHookAttribute.cs
@@ -20,6 +20,9 @@ namespace LeanCloud.Engine {
         }
 
         public LCEngineClassHookAttribute(string className, LCEngineObjectHookType hookType) {
+            if (string.IsNullOrEmpty(className)) {
+                throw new ArgumentNullException(nameof(className));
+            }
             ClassName = className;
             HookType = hookType;
         }
diff --git a/Engine/LCEngine.cs b/Engine/LCEngine.cs
index 7b7b074..2bf6050 100644
--- a/Engine/LCEngine.cs
+++ b/Engine/LCEngine.cs
@@ -9,7 +9,6 @@ using Newtonsoft.Json;
 using Microsoft.Extensions.Primitives;
 using Microsoft.Extensions.DependencyInjection;
 using LeanCloud.Common;
-using LeanCloud.Storage;
 
 namespace LeanCloud.Engine {
     public class LCEngine {
diff --git a/Engine/LCEngineRequestContext.cs b/Engine/LCEngineRequestContext.cs
index 1eb7d8b..c04c2f9 100644
--- a/Engine/LCEngineRequestContext.cs
+++ b/Engine/LCEngineRequestContext.cs
@@ -5,9 +5,9 @@ using LeanCloud.Storage;
 
 namespace LeanCloud.Engine {
     public class LCEngineRequestContext {
-        public const string RemoteAddressKey = "remoteAddressKey";
-        public const string SessionTokenKey = "sessionToken";
-        public const string CurrentUserKey = "currentUser";
+        public const string RemoteAddressKey = "__remoteAddressKey";
+        public const string SessionTokenKey = "__sessionToken";
+        public const string CurrentUserKey = "__currentUser";
 
         private static ThreadLocal<Dictionary<string, object>> requestContext = new ThreadLocal<Dictionary<string, object>>();