From c063fc77e6f0f9578d9f741b5b377c08e5fafba5 Mon Sep 17 00:00:00 2001
From: westey <164392973+westey-m@users.noreply.github.com>
Date: Tue, 13 Jan 2026 19:47:57 +0000
Subject: [PATCH] .NET: Make ChatMessageStore and AIContextProvider context
 props settable (#3196)

* Make ChatMessageStore and AIContextProvider context props setable

* Add validation to preserve non-null requirement of certain properties.

* Fix broken tests.
---
 .../Microsoft.Agents.AI.Abstractions/AIContextProvider.cs | 6 +++---
 .../Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs  | 8 ++++----
 .../src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs | 2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs b/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs
index fd3ff10fc2..f104f12890 100644
--- a/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs
@@ -142,7 +142,7 @@ public abstract class AIContextProvider
         /// <value>
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
     }
 
     /// <summary>
@@ -174,7 +174,7 @@ public abstract class AIContextProvider
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// This does not include any <see cref="AIContextProvider"/> supplied messages.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
 
         /// <summary>
         /// Gets the messages provided by the <see cref="AIContextProvider"/> for this invocation, if any.
@@ -183,7 +183,7 @@ public abstract class AIContextProvider
         /// A collection of <see cref="ChatMessage"/> instances that were provided by the <see cref="AIContextProvider"/>,
         /// and were used by the agent as part of the invocation.
         /// </value>
-        public IEnumerable<ChatMessage>? AIContextProviderMessages { get; }
+        public IEnumerable<ChatMessage>? AIContextProviderMessages { get; set; }
 
         /// <summary>
         /// Gets the collection of response messages generated during this invocation if the invocation succeeded.
diff --git a/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs b/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs
index d28cd191b7..54cee063d7 100644
--- a/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs
@@ -152,7 +152,7 @@ public abstract class ChatMessageStore
         /// <value>
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
     }
 
     /// <summary>
@@ -174,7 +174,7 @@ public abstract class ChatMessageStore
         public InvokedContext(IEnumerable<ChatMessage> requestMessages, IEnumerable<ChatMessage> chatMessageStoreMessages)
         {
             this.RequestMessages = Throw.IfNull(requestMessages);
-            this.ChatMessageStoreMessages = chatMessageStoreMessages;
+            this.ChatMessageStoreMessages = Throw.IfNull(chatMessageStoreMessages);
         }
 
         /// <summary>
@@ -184,7 +184,7 @@ public abstract class ChatMessageStore
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// This does not include any <see cref="ChatMessageStore"/> supplied messages.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
 
         /// <summary>
         /// Gets the messages retrieved from the <see cref="ChatMessageStore"/> for this invocation, if any.
@@ -193,7 +193,7 @@ public abstract class ChatMessageStore
         /// A collection of <see cref="ChatMessage"/> instances that were retrieved from the <see cref="ChatMessageStore"/>,
         /// and were used by the agent as part of the invocation.
         /// </value>
-        public IEnumerable<ChatMessage> ChatMessageStoreMessages { get; }
+        public IEnumerable<ChatMessage> ChatMessageStoreMessages { get; set { field = Throw.IfNull(value); } }
 
         /// <summary>
         /// Gets or sets the messages provided by the <see cref="AIContextProvider"/> for this invocation, if any.
diff --git a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
index 0c02932b0a..8f6d6a5160 100644
--- a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
+++ b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
@@ -692,7 +692,7 @@ public sealed partial class ChatClientAgent : AIAgent
 
         List<ChatMessage> inputMessagesForChatClient = [];
         IList<ChatMessage>? aiContextProviderMessages = null;
-        IList<ChatMessage>? chatMessageStoreMessages = null;
+        IList<ChatMessage>? chatMessageStoreMessages = [];
 
         // Populate the thread messages only if we are not continuing an existing response as it's not allowed
         if (chatOptions?.ContinuationToken is null)