diff --git a/Realtime/Conversation/LCIMChatRoom.cs b/Realtime/Conversation/LCIMChatRoom.cs
index 13919f8..e5f89b3 100644
--- a/Realtime/Conversation/LCIMChatRoom.cs
+++ b/Realtime/Conversation/LCIMChatRoom.cs
@@ -1,18 +1,36 @@
-using System.Collections.ObjectModel;
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Threading.Tasks;
 
 namespace LeanCloud.Realtime {
+    /// <summary>
+    /// 聊天室
+    /// </summary>
     public class LCIMChatRoom : LCIMConversation {
         public LCIMChatRoom(LCIMClient client) :
             base(client) {
         }
 
+        /// <summary>
+        /// 获取在线用户数量
+        /// </summary>
+        /// <returns></returns>
         public async Task<int> GetOnlineMembersCount() {
             return await GetMembersCount();
         }
 
+        /// <summary>
+        /// 获取在线用户
+        /// </summary>
+        /// <param name="limit"></param>
+        /// <returns></returns>
         public async Task<ReadOnlyCollection<string>> GetOnlineMembers(int limit = 50) {
             return await Client.ConversationController.GetOnlineMembers(Id, limit);
         }
+
+        public override Task<LCIMPartiallySuccessResult> AddMembers(IEnumerable<string> clientIds) {
+            throw new Exception("Add members is not allowed in chat room.");
+        }
     }
 }
diff --git a/Realtime/Conversation/LCIMConversation.cs b/Realtime/Conversation/LCIMConversation.cs
index f703d3d..b9556ce 100644
--- a/Realtime/Conversation/LCIMConversation.cs
+++ b/Realtime/Conversation/LCIMConversation.cs
@@ -206,7 +206,7 @@ namespace LeanCloud.Realtime {
         /// </summary>
         /// <param name="clientIds">用户 Id</param>
         /// <returns></returns>
-        public async Task<LCIMPartiallySuccessResult> AddMembers(IEnumerable<string> clientIds) {
+        public virtual async Task<LCIMPartiallySuccessResult> AddMembers(IEnumerable<string> clientIds) {
             if (clientIds == null || clientIds.Count() == 0) {
                 throw new ArgumentNullException(nameof(clientIds));
             }
diff --git a/Realtime/Conversation/LCIMConversationQuery.cs b/Realtime/Conversation/LCIMConversationQuery.cs
index 3e1cfa4..5904ab1 100644
--- a/Realtime/Conversation/LCIMConversationQuery.cs
+++ b/Realtime/Conversation/LCIMConversationQuery.cs
@@ -9,7 +9,7 @@ namespace LeanCloud.Realtime {
             get; private set;
         }
 
-        private LCIMClient client;
+        private readonly LCIMClient client;
 
         public LCIMConversationQuery(LCIMClient client) {
             Condition = new LCCompositionalCondition();
diff --git a/Realtime/Conversation/LCIMServiceConversation.cs b/Realtime/Conversation/LCIMServiceConversation.cs
index b6f52c9..93e8da2 100644
--- a/Realtime/Conversation/LCIMServiceConversation.cs
+++ b/Realtime/Conversation/LCIMServiceConversation.cs
@@ -2,8 +2,23 @@
 using System.Threading.Tasks;
 
 namespace LeanCloud.Realtime {
+    /// <summary>
+    /// 系统对话
+    /// </summary>
     public class LCIMServiceConversation : LCIMConversation {
         public LCIMServiceConversation(LCIMClient client) : base(client) {
         }
+
+        public async Task Subscribe() {
+            await Join();
+        }
+
+        public async Task Unsubscribe() {
+            await Quit();
+        }
+
+        public async Task<bool> CheckSubscription() {
+            return await Client.ConversationController.CheckSubscription(Id);
+        }
     }
 }
diff --git a/Realtime/Conversation/LCIMTemporaryConversation.cs b/Realtime/Conversation/LCIMTemporaryConversation.cs
index 3fc19c3..01f20ad 100644
--- a/Realtime/Conversation/LCIMTemporaryConversation.cs
+++ b/Realtime/Conversation/LCIMTemporaryConversation.cs
@@ -1,11 +1,20 @@
 using System;
 
 namespace LeanCloud.Realtime {
+    /// <summary>
+    /// 临时对话
+    /// </summary>
     public class LCIMTemporaryConversation : LCIMConversation {
+        /// <summary>
+        /// 过期时间
+        /// </summary>
         public DateTime ExpiredAt {
             get;
         }
 
+        /// <summary>
+        /// 是否过期
+        /// </summary>
         public bool IsExpired {
             get {
                 return DateTime.Now > ExpiredAt;
diff --git a/Realtime/Internal/Controller/LCIMConversationController.cs b/Realtime/Internal/Controller/LCIMConversationController.cs
index 79c9f71..019d291 100644
--- a/Realtime/Internal/Controller/LCIMConversationController.cs
+++ b/Realtime/Internal/Controller/LCIMConversationController.cs
@@ -521,6 +521,25 @@ namespace LeanCloud.Realtime.Internal.Controller {
             return members;
         }
 
+        /// <summary>
+        /// 查询是否订阅
+        /// </summary>
+        /// <param name="convId"></param>
+        /// <returns></returns>
+        internal async Task<bool> CheckSubscription(string convId) {
+            ConvCommand conv = new ConvCommand();
+            conv.Cids.Add(convId);
+            GenericCommand request = NewCommand(CommandType.Conv, OpType.IsMember);
+            request.ConvMessage = conv;
+            GenericCommand response = await Client.Connection.SendRequest(request);
+            JsonObjectMessage jsonObj = response.ConvMessage.Results;
+            Dictionary<string, object> result = JsonConvert.DeserializeObject<Dictionary<string, object>>(jsonObj.Data);
+            if (result.TryGetValue(convId, out object obj)) {
+                return (bool)obj;
+            }
+            return false;
+        }
+
         private LCIMPartiallySuccessResult NewPartiallySuccessResult(IEnumerable<string> succesfulIds,
             IEnumerable<ErrorCommand> errors) {
             LCIMPartiallySuccessResult result = new LCIMPartiallySuccessResult {
diff --git a/Test/Realtime.Test/LocalSignatureFactory.cs b/Test/Realtime.Test/LocalSignatureFactory.cs
new file mode 100644
index 0000000..0db73d8
--- /dev/null
+++ b/Test/Realtime.Test/LocalSignatureFactory.cs
@@ -0,0 +1,7 @@
+using System;
+namespace Realtime.Test {
+    public class LocalSignatureFactory {
+        public LocalSignatureFactory() {
+        }
+    }
+}