diff --git a/dotnet/sample/AutoGen.Anthropic.Samples/Anthropic_Agent_With_Prompt_Caching.cs b/dotnet/sample/AutoGen.Anthropic.Samples/Anthropic_Agent_With_Prompt_Caching.cs
index df05ba783ad..5d8a99ce128 100644
--- a/dotnet/sample/AutoGen.Anthropic.Samples/Anthropic_Agent_With_Prompt_Caching.cs
+++ b/dotnet/sample/AutoGen.Anthropic.Samples/Anthropic_Agent_With_Prompt_Caching.cs
@@ -122,13 +122,12 @@ public static async Task RunAsync()
                 new ChatMessage("user", [TextContent.CreateTextWithCacheControl(LongStory)]),
                 from: "user");
 
-        var history =
-            await userProxyAgent.SendMessageToGroupAsync
-            (groupChat,
-                "translate this text for me",
-                new List<IMessage>()
-                {
-                    messageEnvelope
-                });
+        var chatHistory = new List<IMessage>()
+        {
+            new TextMessage(Role.User, "translate this text for me", from: userProxyAgent.Name),
+            messageEnvelope,
+        };
+
+        var history = await groupChat.SendAsync(chatHistory).ToArrayAsync();
     }
 }
diff --git a/dotnet/sample/AutoGen.BasicSamples/Example09_LMStudio_FunctionCall.cs b/dotnet/sample/AutoGen.BasicSamples/Example09_LMStudio_FunctionCall.cs
index c9dda27d2e2..9e20e24df76 100644
--- a/dotnet/sample/AutoGen.BasicSamples/Example09_LMStudio_FunctionCall.cs
+++ b/dotnet/sample/AutoGen.BasicSamples/Example09_LMStudio_FunctionCall.cs
@@ -130,7 +130,8 @@ You are a helpful AI assistant
 
         await userProxyAgent.SendAsync(
             receiver: lmAgent,
-            "Search the names of the five largest stocks in the US by market cap ");
+            "Search the names of the five largest stocks in the US by market cap ")
+            .ToArrayAsync();
         #endregion lmstudio_function_call_example
     }
 }
diff --git a/dotnet/sample/AutoGen.BasicSamples/Example12_TwoAgent_Fill_Application.cs b/dotnet/sample/AutoGen.BasicSamples/Example12_TwoAgent_Fill_Application.cs
index b622a3e641e..ce585f229dc 100644
--- a/dotnet/sample/AutoGen.BasicSamples/Example12_TwoAgent_Fill_Application.cs
+++ b/dotnet/sample/AutoGen.BasicSamples/Example12_TwoAgent_Fill_Application.cs
@@ -120,22 +120,7 @@ public static async Task<IAgent> CreateAssistantAgent()
             modelName: gpt3Config.DeploymentName,
             systemMessage: """You create polite prompt to ask user provide missing information""")
             .RegisterMessageConnector()
-            .RegisterPrintMessage()
-            .RegisterMiddleware(async (msgs, option, agent, ct) =>
-            {
-                var lastReply = msgs.Last() ?? throw new Exception("No reply found.");
-                var reply = await agent.GenerateReplyAsync(msgs, option, ct);
-
-                // if application is complete, exit conversation by sending termination message
-                if (lastReply.GetContent().Contains("Application information is saved to database."))
-                {
-                    return new TextMessage(Role.Assistant, GroupChatExtension.TERMINATE, from: agent.Name);
-                }
-                else
-                {
-                    return reply;
-                }
-            });
+            .RegisterPrintMessage();
 
         return chatAgent;
     }
@@ -191,9 +176,13 @@ public static async Task RunAsync()
         var groupChatManager = new GroupChatManager(groupChat);
         var initialMessage = await assistantAgent.SendAsync("Generate a greeting meesage for user and start the conversation by asking what's their name.");
 
-        var chatHistory = await userAgent.SendAsync(groupChatManager, [initialMessage], maxRound: 30);
-
-        var lastMessage = chatHistory.Last();
-        Console.WriteLine(lastMessage.GetContent());
+        var chatHistory = new List<IMessage> { initialMessage };
+        await foreach (var msg in userAgent.SendAsync(groupChatManager, chatHistory, maxRound: 30))
+        {
+            if (msg.GetContent().ToLower().Contains("application information is saved to database.") is true)
+            {
+                break;
+            }
+        }
     }
 }
diff --git a/dotnet/sample/AutoGen.BasicSamples/GettingStart/FSM_Group_Chat.cs b/dotnet/sample/AutoGen.BasicSamples/GettingStart/FSM_Group_Chat.cs
index 59c0aa9ca88..ac1a1934f07 100644
--- a/dotnet/sample/AutoGen.BasicSamples/GettingStart/FSM_Group_Chat.cs
+++ b/dotnet/sample/AutoGen.BasicSamples/GettingStart/FSM_Group_Chat.cs
@@ -120,22 +120,7 @@ public static async Task<IAgent> CreateAssistantAgent(OpenAIClient openaiClient,
             modelName: model,
             systemMessage: """You create polite prompt to ask user provide missing information""")
             .RegisterMessageConnector()
-            .RegisterPrintMessage()
-            .RegisterMiddleware(async (msgs, option, agent, ct) =>
-            {
-                var lastReply = msgs.Last() ?? throw new Exception("No reply found.");
-                var reply = await agent.GenerateReplyAsync(msgs, option, ct);
-
-                // if application is complete, exit conversation by sending termination message
-                if (lastReply.GetContent()?.Contains("Application information is saved to database.") is true)
-                {
-                    return new TextMessage(Role.Assistant, GroupChatExtension.TERMINATE, from: agent.Name);
-                }
-                else
-                {
-                    return reply;
-                }
-            });
+            .RegisterPrintMessage();
         #endregion Create_Assistant_Agent
         return chatAgent;
     }
@@ -193,9 +178,13 @@ public static async Task RunAsync()
 
         var initialMessage = await assistantAgent.SendAsync("Generate a greeting meesage for user and start the conversation by asking what's their name.");
 
-        var chatHistory = await userAgent.SendMessageToGroupAsync(groupChat, [initialMessage], maxRound: 30);
-
-        var lastMessage = chatHistory.Last();
-        Console.WriteLine(lastMessage.GetContent());
+        var chatHistory = new List<IMessage> { initialMessage };
+        await foreach (var msg in groupChat.SendAsync(chatHistory, maxRound: 30))
+        {
+            if (msg.GetContent().ToLower().Contains("application information is saved to database.") is true)
+            {
+                break;
+            }
+        }
     }
 }
diff --git a/dotnet/src/AutoGen.Core/Extension/AgentExtension.cs b/dotnet/src/AutoGen.Core/Extension/AgentExtension.cs
index 44ce8838b73..13ce970d551 100644
--- a/dotnet/src/AutoGen.Core/Extension/AgentExtension.cs
+++ b/dotnet/src/AutoGen.Core/Extension/AgentExtension.cs
@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // AgentExtension.cs
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -60,14 +61,14 @@ public static async Task<IMessage> SendAsync(
     }
 
     /// <summary>
-    /// Send message to another agent.
+    /// Send message to another agent and iterate over the responses.
     /// </summary>
     /// <param name="agent">sender agent.</param>
     /// <param name="receiver">receiver agent.</param>
     /// <param name="chatHistory">chat history.</param>
     /// <param name="maxRound">max conversation round.</param>
     /// <returns>conversation history</returns>
-    public static async Task<IEnumerable<IMessage>> SendAsync(
+    public static IAsyncEnumerable<IMessage> SendAsync(
         this IAgent agent,
         IAgent receiver,
         IEnumerable<IMessage> chatHistory,
@@ -78,21 +79,21 @@ public static async Task<IEnumerable<IMessage>> SendAsync(
         {
             var gc = manager.GroupChat;
 
-            return await agent.SendMessageToGroupAsync(gc, chatHistory, maxRound, ct);
+            return gc.SendAsync(chatHistory, maxRound, ct);
         }
 
         var groupChat = new RoundRobinGroupChat(
-            agents: new[]
-            {
+            agents:
+            [
                 agent,
                 receiver,
-            });
+            ]);
 
-        return await groupChat.CallAsync(chatHistory, maxRound, ct: ct);
+        return groupChat.SendAsync(chatHistory, maxRound, cancellationToken: ct);
     }
 
     /// <summary>
-    /// Send message to another agent.
+    /// Send message to another agent and iterate over the responses.
     /// </summary>
     /// <param name="agent">sender agent.</param>
     /// <param name="message">message to send. will be added to the end of <paramref name="chatHistory"/> if provided </param>
@@ -100,7 +101,7 @@ public static async Task<IEnumerable<IMessage>> SendAsync(
     /// <param name="chatHistory">chat history.</param>
     /// <param name="maxRound">max conversation round.</param>
     /// <returns>conversation history</returns>
-    public static async Task<IEnumerable<IMessage>> SendAsync(
+    public static IAsyncEnumerable<IMessage> SendAsync(
         this IAgent agent,
         IAgent receiver,
         string message,
@@ -116,11 +117,12 @@ public static async Task<IEnumerable<IMessage>> SendAsync(
         chatHistory = chatHistory ?? new List<IMessage>();
         chatHistory = chatHistory.Append(msg);
 
-        return await agent.SendAsync(receiver, chatHistory, maxRound, ct);
+        return agent.SendAsync(receiver, chatHistory, maxRound, ct);
     }
 
     /// <summary>
-    /// Shortcut API to send message to another agent.
+    /// Shortcut API to send message to another agent and get all responses.
+    /// To iterate over the responses, use <see cref="SendAsync(IAgent, IAgent, string, IEnumerable{IMessage}?, int, CancellationToken)"/> or <see cref="SendAsync(IAgent, IAgent, IEnumerable{IMessage}, int, CancellationToken)"/>
     /// </summary>
     /// <param name="agent">sender agent</param>
     /// <param name="receiver">receiver agent</param>
@@ -144,10 +146,16 @@ public static async Task<IEnumerable<IMessage>> InitiateChatAsync(
             chatHistory.Add(msg);
         }
 
-        return await agent.SendAsync(receiver, chatHistory, maxRound, ct);
+        await foreach (var msg in agent.SendAsync(receiver, chatHistory, maxRound, ct))
+        {
+            chatHistory.Add(msg);
+        }
+
+        return chatHistory;
     }
 
-    public static async Task<IEnumerable<IMessage>> SendMessageToGroupAsync(
+    [Obsolete("use GroupChatExtension.SendAsync")]
+    public static IAsyncEnumerable<IMessage> SendMessageToGroupAsync(
         this IAgent agent,
         IGroupChat groupChat,
         string msg,
@@ -159,16 +167,18 @@ public static async Task<IEnumerable<IMessage>> SendMessageToGroupAsync(
         chatHistory = chatHistory ?? Enumerable.Empty<IMessage>();
         chatHistory = chatHistory.Append(chatMessage);
 
-        return await agent.SendMessageToGroupAsync(groupChat, chatHistory, maxRound, ct);
+        return agent.SendMessageToGroupAsync(groupChat, chatHistory, maxRound, ct);
     }
 
-    public static async Task<IEnumerable<IMessage>> SendMessageToGroupAsync(
+    [Obsolete("use GroupChatExtension.SendAsync")]
+    public static IAsyncEnumerable<IMessage> SendMessageToGroupAsync(
         this IAgent _,
         IGroupChat groupChat,
         IEnumerable<IMessage>? chatHistory = null,
         int maxRound = 10,
         CancellationToken ct = default)
     {
-        return await groupChat.CallAsync(chatHistory, maxRound, ct);
+        chatHistory = chatHistory ?? Enumerable.Empty<IMessage>();
+        return groupChat.SendAsync(chatHistory, maxRound, ct);
     }
 }