diff --git a/Realtime/Realtime/Conversation/LCIMChatRoom.cs b/Realtime/Realtime/Conversation/LCIMChatRoom.cs
index 5b77f92..0ecccf1 100644
--- a/Realtime/Realtime/Conversation/LCIMChatRoom.cs
+++ b/Realtime/Realtime/Conversation/LCIMChatRoom.cs
@@ -32,5 +32,9 @@ namespace LeanCloud.Realtime {
         public override Task Read() {
             return Task.CompletedTask;
         }
+
+        public override Task FetchReciptTimestamps() {
+            return Task.CompletedTask;
+        }
     }
 }
diff --git a/Realtime/Realtime/Conversation/LCIMConversation.cs b/Realtime/Realtime/Conversation/LCIMConversation.cs
index c2553d5..f74ace8 100644
--- a/Realtime/Realtime/Conversation/LCIMConversation.cs
+++ b/Realtime/Realtime/Conversation/LCIMConversation.cs
@@ -467,7 +467,7 @@ namespace LeanCloud.Realtime {
         /// Fetches receipt timestamp.
         /// </summary>
         /// <returns></returns>
-        public async Task FetchReciptTimestamps() {
+        public virtual async Task FetchReciptTimestamps() {
             await Client.ConversationController.FetchReciptTimestamp(Id);
         }
 
diff --git a/Realtime/Realtime/Conversation/LCIMServiceConversation.cs b/Realtime/Realtime/Conversation/LCIMServiceConversation.cs
index b2159a6..d55a16f 100644
--- a/Realtime/Realtime/Conversation/LCIMServiceConversation.cs
+++ b/Realtime/Realtime/Conversation/LCIMServiceConversation.cs
@@ -17,5 +17,9 @@ namespace LeanCloud.Realtime {
         public async Task<bool> CheckSubscription() {
             return await Client.ConversationController.CheckSubscription(Id);
         }
+
+        public override Task FetchReciptTimestamps() {
+            return Task.CompletedTask;
+        }
     }
 }
diff --git a/Realtime/Realtime/Message/LCIMMessage.cs b/Realtime/Realtime/Message/LCIMMessage.cs
index 4652845..85bdf01 100644
--- a/Realtime/Realtime/Message/LCIMMessage.cs
+++ b/Realtime/Realtime/Message/LCIMMessage.cs
@@ -120,8 +120,8 @@ namespace LeanCloud.Realtime {
         /// <summary>
         /// Indicates whether this message is transient.
         /// </summary>
-        public bool IsTransient {
-            get; internal set;
+        internal bool IsTransient {
+            get; set;
         }
 
         internal LCIMMessage() {
diff --git a/Storage/Storage/LCQuery.cs b/Storage/Storage/LCQuery.cs
index 928bc1e..c9396f7 100644
--- a/Storage/Storage/LCQuery.cs
+++ b/Storage/Storage/LCQuery.cs
@@ -346,12 +346,13 @@ namespace LeanCloud.Storage {
             return (int)ret["count"];
         }
 
-        public Task<T> Get(string objectId) {
+        public async Task<T> Get(string objectId) {
             if (string.IsNullOrEmpty(objectId)) {
                 throw new ArgumentNullException(nameof(objectId));
             }
-            WhereEqualTo("objectId", objectId);
-            return First();
+            string path = $"classes/{ClassName}/{objectId}";
+            Dictionary<string, object> response = await LCApplication.HttpClient.Get<Dictionary<string, object>>(path);
+            return DecodeLCObject(response);
         }
 
         public async Task<ReadOnlyCollection<T>> Find() {
@@ -361,9 +362,7 @@ namespace LeanCloud.Storage {
             List<object> results = response["results"] as List<object>;
             List<T> list = new List<T>();
             foreach (object item in results) {
-                LCObjectData objectData = LCObjectData.Decode(item as Dictionary<string, object>);
-                T obj = LCObject.Create(ClassName) as T;
-                obj.Merge(objectData);
+                T obj = DecodeLCObject(item as Dictionary<string, object>);
                 list.Add(obj);
             }
             return list.AsReadOnly();
@@ -412,5 +411,12 @@ namespace LeanCloud.Storage {
             compositionQuery.ClassName = className;
             return compositionQuery;
         }
+
+        private T DecodeLCObject(Dictionary<string, object> data) {
+            LCObjectData objectData = LCObjectData.Decode(data);
+            T obj = LCObject.Create(ClassName) as T;
+            obj.Merge(objectData);
+            return obj;
+        }
     }
 }
diff --git a/Storage/Storage/LCUser.cs b/Storage/Storage/LCUser.cs
index af1aa03..70e8f28 100644
--- a/Storage/Storage/LCUser.cs
+++ b/Storage/Storage/LCUser.cs
@@ -326,7 +326,7 @@ namespace LeanCloud.Storage {
             if (string.IsNullOrEmpty(platform)) {
                 throw new ArgumentNullException(nameof(platform));
             }
-            return LinkWithAuthData(platform, null);
+            return UnlinkWithAuthData(platform);
         }
 
         /// <summary>
@@ -523,11 +523,34 @@ namespace LeanCloud.Storage {
             return new LCQuery<LCUser>(CLASS_NAME);
         }
 
-        Task LinkWithAuthData(string authType, Dictionary<string, object> data) {
+        async Task LinkWithAuthData(string authType, Dictionary<string, object> data) {
+            Dictionary<string, object> oriAuthData = new Dictionary<string, object>(AuthData);
             AuthData = new Dictionary<string, object> {
                 { authType, data }
             };
-            return Save();
+            try {
+                await Save();
+                oriAuthData.Add(authType, data);
+                AuthData = oriAuthData;
+            } catch (Exception e) {
+                AuthData = oriAuthData;
+                throw e;
+            }
+        }
+
+        async Task UnlinkWithAuthData(string authType) {
+            Dictionary<string, object> oriAuthData = new Dictionary<string, object>(AuthData);
+            AuthData = new Dictionary<string, object> {
+                { authType, null }
+            };
+            try {
+                await Save();
+                oriAuthData.Remove(authType);
+                AuthData = oriAuthData;
+            } catch (Exception e) {
+                AuthData = oriAuthData;
+                throw e;
+            }
         }
 
         static async Task<LCUser> Login(Dictionary<string, object> data) {
diff --git a/Storage/Storage/Leaderboard/LCLeaderboard.cs b/Storage/Storage/Leaderboard/LCLeaderboard.cs
index 8062563..29b39b7 100644
--- a/Storage/Storage/Leaderboard/LCLeaderboard.cs
+++ b/Storage/Storage/Leaderboard/LCLeaderboard.cs
@@ -97,7 +97,7 @@ namespace LeanCloud.Storage {
 
         public static async Task<ReadOnlyCollection<LCStatistic>> UpdateStatistics(LCUser user,
             Dictionary<string, double> statistics,
-            bool overwrite = true) {
+            bool overwrite = false) {
             if (user == null) {
                 throw new ArgumentNullException(nameof(user));
             }