diff --git a/Common/Common/Persistence/PersistenceController.cs b/Common/Common/Persistence/PersistenceController.cs
index 46a76c1..a3c494b 100644
--- a/Common/Common/Persistence/PersistenceController.cs
+++ b/Common/Common/Persistence/PersistenceController.cs
@@ -19,7 +19,7 @@ namespace LeanCloud.Common {
             }
 
             string path = GetFileFullPath(filename);
-            using (FileStream fs = IOFile.OpenWrite(path)) {
+            using (FileStream fs = IOFile.Create(path)) {
                 byte[] buffer = Encoding.UTF8.GetBytes(text);
                 await fs.WriteAsync(buffer, 0, buffer.Length);
             }
diff --git a/Storage/Storage/Public/LCObject.cs b/Storage/Storage/Public/LCObject.cs
index 38d5e9c..62868ea 100644
--- a/Storage/Storage/Public/LCObject.cs
+++ b/Storage/Storage/Public/LCObject.cs
@@ -572,8 +572,8 @@ namespace LeanCloud.Storage {
         public void Merge(LCObjectData objectData) {
             data.ClassName = objectData.ClassName ?? data.ClassName;
             data.ObjectId = objectData.ObjectId ?? data.ObjectId;
-            data.CreatedAt = objectData.CreatedAt != null ? objectData.CreatedAt : data.CreatedAt;
-            data.UpdatedAt = objectData.UpdatedAt != null ? objectData.UpdatedAt : data.UpdatedAt;
+            data.CreatedAt = !objectData.CreatedAt.Equals(default) ? objectData.CreatedAt : data.CreatedAt;
+            data.UpdatedAt = !objectData.UpdatedAt.Equals(default) ? objectData.UpdatedAt : data.UpdatedAt;
             // 先将本地的预估数据直接替换
             data.CustomPropertyDict = estimatedData;
             // 再将服务端的数据覆盖
diff --git a/Storage/Storage/Public/LCUser.cs b/Storage/Storage/Public/LCUser.cs
index ef0957e..ea8143d 100644
--- a/Storage/Storage/Public/LCUser.cs
+++ b/Storage/Storage/Public/LCUser.cs
@@ -127,9 +127,6 @@ namespace LeanCloud.Storage {
                 throw new ArgumentException("Cannot sign up a user that already exists.");
             }
             await Save();
-            currentUser = this;
-
-            await SaveToLocal();
 
             return this;
         }
@@ -555,7 +552,7 @@ namespace LeanCloud.Storage {
                 { authType, data }
             };
             try {
-                await Save();
+                await base.Save();
                 oriAuthData[authType] = data;
                 await UpdateAuthData(oriAuthData);
             } catch (Exception e) {
@@ -570,7 +567,7 @@ namespace LeanCloud.Storage {
                 { authType, null }
             };
             try {
-                await Save();
+                await base.Save();
                 oriAuthData.Remove(authType);
                 await UpdateAuthData(oriAuthData);
             } catch (Exception e) {
@@ -765,5 +762,12 @@ namespace LeanCloud.Storage {
             }
             return result;
         }
+
+        public new async Task<LCUser> Save(bool fetchWhenSave = false, LCQuery<LCObject> query = null) {
+            await base.Save(fetchWhenSave, query);
+            currentUser = this;
+            await SaveToLocal();
+            return this;
+        }
     }
 }