.NET: Remove AgentThread.GetMessagesAsync (#668)

* Remove AgentThread.GetMessagesAsync

* Remove unecessary using

dotnet/src/Microsoft.Agents.Orchestration/OrchestratingAgent.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text.Json;
 using System.Threading;
@@ -75,11 +76,7 @@ public abstract partial class OrchestratingAgent : AIAgent
                 throw new InvalidOperationException("An agent service managed thread is not supported by this agent.");
             }
 
-            List<ChatMessage> messagesList = [];
+            List<ChatMessage> messagesList = (await thread.MessageStore.GetMessagesAsync(cancellationToken).ConfigureAwait(false)).ToList();
-            await foreach (var threadMessage in thread.GetMessagesAsync(cancellationToken).ConfigureAwait(false))
-            {
-                messagesList.Add(threadMessage);
-            }
             messagesList.AddRange(messages);
             messages = messagesList;
         }

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/AgentThread.cs

@@ -3,7 +3,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Runtime.CompilerServices;
 using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
@@ -109,23 +108,6 @@ public class AgentThread
         }
     }
 
-    /// <summary>
-    /// Retrieves any messages stored in the <see cref="IChatMessageStore"/> of the thread, otherwise returns an empty collection.
-    /// </summary>
-    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
-    /// <returns>The messages from the <see cref="IChatMessageStore"/> in ascending chronological order, with the oldest message first.</returns>
-    public virtual async IAsyncEnumerable<ChatMessage> GetMessagesAsync([EnumeratorCancellation] CancellationToken cancellationToken = default)
-    {
-        if (this._messageStore is not null)
-        {
-            var messages = await this._messageStore!.GetMessagesAsync(cancellationToken).ConfigureAwait(false);
-            foreach (var message in messages)
-            {
-                yield return message;
-            }
-        }
-    }
-
     /// <summary>
     /// Serializes the current object's state to a <see cref="JsonElement"/> using the specified serialization options.
     /// </summary>

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/IChatMessageStore.cs

@@ -34,7 +34,7 @@ public interface IChatMessageStore
     /// since they may contain state that is specific to a thread.
     /// </para>
     /// </remarks>
-    Task<IEnumerable<ChatMessage>> GetMessagesAsync(CancellationToken cancellationToken);
+    Task<IEnumerable<ChatMessage>> GetMessagesAsync(CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Adds messages to the store.
@@ -42,7 +42,7 @@ public interface IChatMessageStore
     /// <param name="messages">The messages to add.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>An async task.</returns>
-    Task AddMessagesAsync(IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken);
+    Task AddMessagesAsync(IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Deserializes the state contained in the provided <see cref="JsonElement"/> into the properties on this store.

dotnet/src/Microsoft.Extensions.AI.Agents/ChatCompletion/ChatClientAgent.cs

@@ -344,9 +344,9 @@ public sealed class ChatClientAgent : AIAgent
 
         // Add any existing messages from the thread to the messages to be sent to the chat client.
         List<ChatMessage> threadMessages = [];
-        await foreach (ChatMessage message in thread.GetMessagesAsync(cancellationToken).ConfigureAwait(false))
+        if (thread.MessageStore is not null)
         {
-            threadMessages.Add(message);
+            threadMessages.AddRange(await thread.MessageStore.GetMessagesAsync(cancellationToken).ConfigureAwait(false));
         }
 
         // Add the input messages to the end of thread messages.

dotnet/tests/Microsoft.Extensions.AI.Agents.Abstractions.UnitTests/AgentThreadTests.cs

@@ -88,56 +88,6 @@ public class AgentThreadTests
 
     #endregion Constructor and Property Tests
 
-    #region GetMessagesAsync Tests
-
-    [Fact]
-    public async Task GetMessagesAsyncReturnsEmptyListWhenNoStoreAsync()
-    {
-        // Arrange
-        var thread = new AgentThread();
-
-        // Act
-        var messages = await ToListAsync(thread.GetMessagesAsync(CancellationToken.None));
-
-        // Assert
-        Assert.Empty(messages);
-    }
-
-    [Fact]
-    public async Task GetMessagesAsyncReturnsEmptyListWhenAgentServiceIdAsync()
-    {
-        // Arrange
-        var thread = new AgentThread { ConversationId = "thread-123" };
-
-        // Act
-        var messages = await ToListAsync(thread.GetMessagesAsync(CancellationToken.None));
-
-        // Assert
-        Assert.Empty(messages);
-    }
-
-    [Fact]
-    public async Task GetMessagesAsyncReturnsMessagesFromStoreAsync()
-    {
-        // Arrange
-        var store = new InMemoryChatMessageStore
-        {
-            new ChatMessage(ChatRole.User, "Hello"),
-            new ChatMessage(ChatRole.Assistant, "Hi there!")
-        };
-        var thread = new AgentThread { MessageStore = store };
-
-        // Act
-        var messages = await ToListAsync(thread.GetMessagesAsync(CancellationToken.None));
-
-        // Assert
-        Assert.Equal(2, messages.Count);
-        Assert.Equal("Hello", messages[0].Text);
-        Assert.Equal("Hi there!", messages[1].Text);
-    }
-
-    #endregion GetMessagesAsync Tests
-
     #region OnNewMessagesAsync Tests
 
     [Fact]

dotnet/tests/OpenAIChatCompletion.IntegrationTests/OpenAIChatCompletionFixture.cs

@@ -32,7 +32,7 @@ public class OpenAIChatCompletionFixture : IChatClientAgentFixture
 
     public async Task<List<ChatMessage>> GetChatHistoryAsync(AgentThread thread)
     {
-        return await thread.GetMessagesAsync().ToListAsync();
+        return thread.MessageStore is null ? [] : (await thread.MessageStore.GetMessagesAsync()).ToList();
     }
 
     public Task<ChatClientAgent> CreateChatClientAgentAsync(

dotnet/tests/OpenAIResponse.IntegrationTests/OpenAIResponseFixture.cs

@@ -50,7 +50,7 @@ public class OpenAIResponseFixture(bool store) : IChatClientAgentFixture
             return [.. previousMessages, responseMessage];
         }
 
-        return await thread.GetMessagesAsync().ToListAsync();
+        return thread.MessageStore is null ? [] : (await thread.MessageStore.GetMessagesAsync()).ToList();
     }
 
     private static ChatMessage ConvertToChatMessage(ResponseItem item)