diff --git a/Realtime/Conversation/LCIMConversation.cs b/Realtime/Conversation/LCIMConversation.cs
index b9556ce..2e40ddc 100644
--- a/Realtime/Conversation/LCIMConversation.cs
+++ b/Realtime/Conversation/LCIMConversation.cs
@@ -164,6 +164,9 @@ namespace LeanCloud.Realtime {
         internal LCIMConversation(LCIMClient client) {
             Client = client;
             customProperties = new Dictionary<string, object>();
+            ids = new HashSet<string>();
+            mutedIds = new HashSet<string>();
+            customProperties = new Dictionary<string, object>();
         }
 
         /// <summary>
@@ -210,7 +213,9 @@ namespace LeanCloud.Realtime {
             if (clientIds == null || clientIds.Count() == 0) {
                 throw new ArgumentNullException(nameof(clientIds));
             }
-            return await Client.ConversationController.AddMembers(Id, clientIds);
+            LCIMPartiallySuccessResult result = await Client.ConversationController.AddMembers(Id, clientIds);
+            ids.UnionWith(result.SuccessfulClientIdList);
+            return result;
         }
 
         /// <summary>
@@ -222,7 +227,9 @@ namespace LeanCloud.Realtime {
             if (removeIds == null || removeIds.Count() == 0) {
                 throw new ArgumentNullException(nameof(removeIds));
             }
-            return await Client.ConversationController.RemoveMembers(Id, removeIds);
+            LCIMPartiallySuccessResult result = await Client.ConversationController.RemoveMembers(Id, removeIds);
+            ids.RemoveWhere(id => result.SuccessfulClientIdList.Contains(id));
+            return result;
         }
 
         /// <summary>
@@ -294,7 +301,11 @@ namespace LeanCloud.Realtime {
             if (clientIds == null || clientIds.Count() == 0) {
                 throw new ArgumentNullException(nameof(clientIds));
             }
-            return await Client.ConversationController.MuteMembers(Id, clientIds);
+            LCIMPartiallySuccessResult result = await Client.ConversationController.MuteMembers(Id, clientIds);
+            if (result.SuccessfulClientIdList != null) {
+                mutedIds.UnionWith(result.SuccessfulClientIdList);
+            }
+            return result;
         }
 
         /// <summary>
@@ -306,7 +317,11 @@ namespace LeanCloud.Realtime {
             if (clientIds == null || clientIds.Count() == 0) {
                 throw new ArgumentNullException(nameof(clientIds));
             }
-            return await Client.ConversationController.UnmuteMembers(Id, clientIds);
+            LCIMPartiallySuccessResult result = await Client.ConversationController.UnmuteMembers(Id, clientIds);
+            if (result.SuccessfulClientIdList != null) {
+                mutedIds.RemoveWhere(id => result.SuccessfulClientIdList.Contains(id));
+            }
+            return result;
         }
 
         /// <summary>
diff --git a/Realtime/Internal/Controller/LCIMConversationController.cs b/Realtime/Internal/Controller/LCIMConversationController.cs
index 019d291..4029254 100644
--- a/Realtime/Internal/Controller/LCIMConversationController.cs
+++ b/Realtime/Internal/Controller/LCIMConversationController.cs
@@ -375,9 +375,11 @@ namespace LeanCloud.Realtime.Internal.Controller {
             string next = null) {
             ConvCommand conv = new ConvCommand {
                 Cid = convId,
-                Limit = limit,
-                Next = next
+                Limit = limit
             };
+            if (next != null) {
+                conv.Next = next;
+            }
             GenericCommand request = NewCommand(CommandType.Conv, OpType.QueryShutup);
             request.ConvMessage = conv;
             GenericCommand response = await Client.Connection.SendRequest(request);
@@ -399,9 +401,11 @@ namespace LeanCloud.Realtime.Internal.Controller {
             string next = null) {
             BlacklistCommand black = new BlacklistCommand {
                 SrcCid = convId,
-                Limit = limit,
-                Next = next
+                Limit = limit
             };
+            if (next != null) {
+                black.Next = next;
+            }
             GenericCommand request = NewCommand(CommandType.Blacklist, OpType.Query);
             request.BlacklistMessage = black;
             GenericCommand response = await Client.Connection.SendRequest(request);
@@ -620,7 +624,7 @@ namespace LeanCloud.Realtime.Internal.Controller {
         private async Task OnMembersJoined(ConvCommand convMessage) {
             LCIMConversation conversation = await Client.GetOrQueryConversation(convMessage.Cid);
             ReadOnlyCollection<string> joinedIds = new ReadOnlyCollection<string>(convMessage.M);
-            conversation.ids.Union(joinedIds);
+            conversation.ids.UnionWith(joinedIds);
             Client.OnMembersJoined?.Invoke(conversation, joinedIds, convMessage.InitBy);
         }
 
@@ -666,7 +670,7 @@ namespace LeanCloud.Realtime.Internal.Controller {
         private async Task OnMembersMuted(ConvCommand convMessage) {
             LCIMConversation conversation = await Client.GetOrQueryConversation(convMessage.Cid);
             ReadOnlyCollection<string> mutedMemberIds = new ReadOnlyCollection<string>(convMessage.M);
-            conversation.mutedIds.Union(mutedMemberIds);
+            conversation.mutedIds.UnionWith(mutedMemberIds);
             Client.OnMembersMuted?.Invoke(conversation, mutedMemberIds, convMessage.InitBy);
         }