Now serializing empty lists

src/libraries/Core/Microsoft.Agents.Core/Models/Activity.cs

@@ -35,6 +35,14 @@ public class Activity :
         /// <summary> Initializes a new instance of Activity. </summary>
         public Activity()
         {
+            MembersAdded = [];
+            MembersRemoved = [];
+            ReactionsAdded = [];
+            ReactionsRemoved = [];
+            Attachments = [];
+            Entities = [];
+            ListenFor = [];
+            TextHighlights = [];
         }
 
         /// <summary> Initializes a new instance of Activity. </summary>
@@ -98,19 +106,19 @@ public Activity(string type = default, string id = default, System.DateTimeOffse
             Recipient = recipient;
             TextFormat = textFormat;
             AttachmentLayout = attachmentLayout;
-            MembersAdded = membersAdded;
-            MembersRemoved = membersRemoved;
-            ReactionsAdded = reactionsAdded;
-            ReactionsRemoved = reactionsRemoved;
+            MembersAdded = membersAdded ?? [];
+            MembersRemoved = membersRemoved ?? [];
+            ReactionsAdded = reactionsAdded ?? [];
+            ReactionsRemoved = reactionsRemoved ?? [];
             TopicName = topicName;
             Locale = locale;
             Text = text;
             Speak = speak;
             InputHint = inputHint;
             Summary = summary;
             SuggestedActions = suggestedActions;
-            Attachments = attachments;
-            Entities = entities;
+            Attachments = attachments ?? [];
+            Entities = entities ?? [];
             ChannelData = channelData;
             Action = action;
             ReplyToId = replyToId;
@@ -123,8 +131,8 @@ public Activity(string type = default, string id = default, System.DateTimeOffse
             Expiration = expiration;
             Importance = importance;
             DeliveryMode = deliveryMode;
-            ListenFor = listenFor;
-            TextHighlights = textHighlights;
+            ListenFor = listenFor ?? [];
+            TextHighlights = textHighlights ?? [];
             SemanticAction = semanticAction;
         }
 

src/libraries/Core/Microsoft.Agents.Core/Models/BasicCard.cs

@@ -29,8 +29,8 @@ public BasicCard(string title = default, string subtitle = default, string text
             Title = title;
             Subtitle = subtitle;
             Text = text;
-            Images = images;
-            Buttons = buttons;
+            Images = images ?? [];
+            Buttons = buttons ?? [];
             Tap = tap;
         }
 

src/libraries/Core/Microsoft.Agents.Core/Models/VideoCard.cs

@@ -10,7 +10,11 @@ namespace Microsoft.Agents.Core.Models
     /// <summary> Video card. </summary>
     public class VideoCard
     {
-        public VideoCard() { }
+        public VideoCard() 
+        {
+            Media = [];
+            Buttons = [];
+        }
 
         /// <summary> Initializes a new instance of VideoCard. </summary>
         /// <param name="title"> Title of this card. </param>

src/libraries/Core/Microsoft.Agents.Core/Serialization/Converters/ConnectorConverter.cs

@@ -65,14 +65,15 @@ public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions
                 {
                     var propertyValue = property.GetValue(value);
 
+#if SKIP_EMPTY_LISTS
                     if (propertyValue is IList list)
                     {
                         if (list == null || list.Count == 0)
                         {
                             continue;
                         }
                     }
-
+#endif
                     if (propertyValue != null || !(options.DefaultIgnoreCondition == JsonIgnoreCondition.WhenWritingNull))
 
                     {
@@ -267,6 +268,7 @@ private void ReadProperty(ref Utf8JsonReader reader, T value, string propertyNam
                 var CollectionPropertyValue = System.Text.Json.JsonSerializer.Deserialize(ref reader, property.PropertyType, options);
                 if (CollectionPropertyValue is IList prospectiveList)
                 {
+#if SKIP_EMPTY_LISTS
                     if (prospectiveList.Count != 0)
                     {
                         property.SetValue(value, CollectionPropertyValue);
@@ -275,6 +277,9 @@ private void ReadProperty(ref Utf8JsonReader reader, T value, string propertyNam
                     {
                         property.SetValue(value, null);
                     }
+#else
+                    property.SetValue(value, CollectionPropertyValue);
+#endif
                 }
                 return;
             }

src/libraries/Extensions/Microsoft.Agents.Extensions.Teams/Serialization/Converters/MessagingExtensionAttachmentConverter.cs

@@ -1,14 +1,57 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+using Microsoft.Agents.Core.Serialization;
 using Microsoft.Agents.Core.Serialization.Converters;
 using Microsoft.Agents.Extensions.Teams.Models;
+using System.Text.Json;
 
 namespace Microsoft.Agents.Extensions.Teams.Serialization.Converters
 {
     // This is required because ConnectorConverter supports derived type handling.
     // In this case for the 'Task' property of type TaskModuleResponseBase.
     internal class MessagingExtensionAttachmentConverter : ConnectorConverter<MessagingExtensionAttachment>
     {
+        /// <inheritdoc/>
+        protected override void ReadExtensionData(ref Utf8JsonReader reader, MessagingExtensionAttachment value, string propertyName, JsonSerializerOptions options)
+        {
+            var extensionData = JsonSerializer.Deserialize<JsonElement>(ref reader, options);
+            value.Properties.Add(propertyName, extensionData);
+        }
+
+        /// <inheritdoc/>
+        protected override bool TryReadExtensionData(ref Utf8JsonReader reader, MessagingExtensionAttachment value, string propertyName, JsonSerializerOptions options)
+        {
+            if (!propertyName.Equals(nameof(value.Properties)))
+            {
+                return false;
+            }
+
+            var propertyValue = JsonSerializer.Deserialize<object>(ref reader, options);
+
+            foreach (var element in propertyValue.ToJsonElements())
+            {
+                value.Properties.Add(element.Key, element.Value);
+            }
+
+            return true;
+        }
+
+        /// <inheritdoc/>
+        protected override bool TryWriteExtensionData(Utf8JsonWriter writer, MessagingExtensionAttachment value, string propertyName)
+        {
+            if (!propertyName.Equals(nameof(value.Properties)))
+            {
+                return false;
+            }
+
+            foreach (var extensionData in value.Properties)
+            {
+                writer.WritePropertyName(extensionData.Key);
+                extensionData.Value.WriteTo(writer);
+            }
+
+            return true;
+        }
     }
 }

src/tests/Microsoft.Agents.Extensions.Teams.Tests/Model/TestJson/MessagingExtensionAction.json

@@ -1 +1 @@
-{"commandId":"commandId","commandContext":"commandContext","botMessagePreviewAction":"botMessagePreviewAction","botActivityPreview":[{"type":"message"}],"messagePayload":{"id":"id","replyToId":"replyToId","messageType":"messageType","createdDateTime":"2025-06-15T13:45:30","lastModifiedDateTime":"2025-07-17T14:46:40","deleted":false,"subject":"subject","summary":"summary","importance":"importance","locale":"locale","from":{"user":{"userIdentityType":"userIdentityType","id":"id","displayName":"displayName"},"application":{"applicationIdentityType":"applicationIdentityType","id":"id","displayName":"displayName"},"conversation":{"conversationIdentityType":"conversationIdentityType","id":"id","displayName":"displayName"}},"body":{"contentType":"contentType","content":"content"},"attachmentLayout":"attachmentLayout","attachments":[{"id":"id","contentType":"contentType","contentUrl":"contentUrl","content":"content","name":"name","thumbnailUrl":"thumbnailUrl"}],"mentions":[{"id":1,"mentionText":"mentionText","mentioned":{}}],"reactions":[{"reactionType":"reactionType","createdDateTime":"createdDateTime","user":{}}]}}
+{"commandId":"commandId","commandContext":"commandContext","botMessagePreviewAction":"botMessagePreviewAction","botActivityPreview":[{"type":"message","membersAdded":[],"membersRemoved":[],"reactionsAdded":[],"reactionsRemoved":[],"attachments":[],"entities":[],"listenFor":[],"textHighlights":[]}],"messagePayload":{"id":"id","replyToId":"replyToId","messageType":"messageType","createdDateTime":"2025-06-15T13:45:30","lastModifiedDateTime":"2025-07-17T14:46:40","deleted":false,"subject":"subject","summary":"summary","importance":"importance","locale":"locale","from":{"user":{"userIdentityType":"userIdentityType","id":"id","displayName":"displayName"},"application":{"applicationIdentityType":"applicationIdentityType","id":"id","displayName":"displayName"},"conversation":{"conversationIdentityType":"conversationIdentityType","id":"id","displayName":"displayName"}},"body":{"contentType":"contentType","content":"content"},"attachmentLayout":"attachmentLayout","attachments":[{"id":"id","contentType":"contentType","contentUrl":"contentUrl","content":"content","name":"name","thumbnailUrl":"thumbnailUrl"}],"mentions":[{"id":1,"mentionText":"mentionText","mentioned":{}}],"reactions":[{"reactionType":"reactionType","createdDateTime":"createdDateTime","user":{}}]}}

src/tests/Microsoft.Agents.Extensions.Teams.Tests/Model/TestJson/MessagingExtensionActionResponse.json

@@ -1 +1 @@
-{"task":{"type":"message","prop1":"prop1"},"composeExtension":{"attachmentLayout":"attachmentLayout","type":"type","attachments":[{"properties":{}}],"suggestedActions":{"actions":[{"type":"type","title":"title","image":"image","imageAltText":"imageAltText","text":"text","displayText":"displayText","value":{"value":"value"},"channelData":{"channelData":"channelData"}}]},"text":"text","activityPreview":{}},"cacheInfo":{"cacheType":"cacheType","cacheDuration":1}}
+{"task":{"type":"message","prop1":"prop1"},"composeExtension":{"attachmentLayout":"attachmentLayout","type":"type","attachments":[{}],"suggestedActions":{"actions":[{"type":"type","title":"title","image":"image","imageAltText":"imageAltText","text":"text","displayText":"displayText","value":{"value":"value"},"channelData":{"channelData":"channelData"}}]},"text":"text","activityPreview":{"membersAdded":[],"membersRemoved":[],"reactionsAdded":[],"reactionsRemoved":[],"attachments":[],"entities":[],"listenFor":[],"textHighlights":[]}},"cacheInfo":{"cacheType":"cacheType","cacheDuration":1}}

src/tests/Microsoft.Agents.Model.Tests/ConversationParametersTests.cs

@@ -25,7 +25,11 @@ public void ConversationParametersRoundTrip()
             var outJson = ProtocolJsonSerializer.ToJson(outConversation);
 
             // Specifically, should include: "bot": {} and not "agent": {}
+#if SKIP_EMPTY_LISTS
             var outExpected = "{\"isGroup\":false,\"bot\":{\"id\":\"agent\"},\"members\":[{\"id\":\"member\"}],\"topicName\":\"topicName\",\"tenantId\":\"tenantId\",\"activity\":{\"type\":\"message\"}}";
+#else
+            var outExpected = "{\"isGroup\":false,\"bot\":{\"id\":\"agent\"},\"members\":[{\"id\":\"member\"}],\"topicName\":\"topicName\",\"tenantId\":\"tenantId\",\"activity\":{\"type\":\"message\",\"membersAdded\":[],\"membersRemoved\":[],\"reactionsAdded\":[],\"reactionsRemoved\":[],\"attachments\":[],\"entities\":[],\"listenFor\":[],\"textHighlights\":[]}}";
+#endif
 
             Assert.Equal(outExpected, outJson);
 

src/tests/Microsoft.Agents.Model.Tests/ConversationReferenceTests.cs

@@ -58,7 +58,11 @@ public void InActivityConversationReferenceSerialize()
             };
 
             var outJson = ProtocolJsonSerializer.ToJson(activity);
+#if SKIP_EMPTY_LISTS
             var outExpected = "{\"relatesTo\":{\"activityId\":\"id\",\"user\":{\"id\":\"user\"},\"bot\":{\"id\":\"agent\"},\"conversation\":{\"id\":\"conversation\"},\"channelId\":\"channelId\",\"serviceUrl\":\"serviceUrl\",\"locale\":\"locale\"}}";
+#else
+            var outExpected = "{\"membersAdded\":[],\"membersRemoved\":[],\"reactionsAdded\":[],\"reactionsRemoved\":[],\"attachments\":[],\"entities\":[],\"relatesTo\":{\"activityId\":\"id\",\"user\":{\"id\":\"user\"},\"bot\":{\"id\":\"agent\"},\"conversation\":{\"id\":\"conversation\"},\"channelId\":\"channelId\",\"serviceUrl\":\"serviceUrl\",\"locale\":\"locale\"},\"listenFor\":[],\"textHighlights\":[]}";
+#endif
             Assert.Equal(outExpected, outJson);
         }
     }

src/tests/Microsoft.Agents.Model.Tests/ObjectSerializationTests.cs

@@ -362,6 +362,7 @@ public void ValidateActivitySerializer(string baseFileName)
             Assert.Equal(resultingText, outboundJson);
         }
 
+#if SKIP_EMPTY_LISTS
         [Fact]
         public void EmptyListDoesntSerialzie()
         {
@@ -386,7 +387,7 @@ public void EmptyListDoesntSerialzie()
             var expected = "{\"suggestedActions\":{\"to\":[\"test\"]}}";
             Assert.Equal(expected, json);
         }
-
+#endif
 
         private Activity RoundTrip(Activity outActivity)
         {
@@ -408,6 +409,10 @@ private void AssertPropertyValues(Activity activity)
             Assert.NotEmpty(activity.ReactionsAdded);
             Assert.NotEmpty(activity.ReactionsRemoved);
 
+            Assert.NotNull(activity.Attachments);
+            Assert.NotNull(activity.ListenFor);
+            Assert.NotNull(activity.TextHighlights);
+
             // validate .value, .channeldata and the activity additional properties are present
             Assert.NotNull(activity.Value);
             var valueTestObject = ProtocolJsonSerializer.ToObject<TestObjectClass>(activity.Value);

src/tests/Microsoft.Agents.Model.Tests/Resources/ComplexActivityPayload.json

@@ -47,7 +47,6 @@
   ],
   "locale": "en-US",
   "text": "validation",
-  "attachments": [],
   "entities": [
     {
       "type": "ClientCapabilities",
@@ -77,7 +76,7 @@
       "TestObject": null
     }
   },
-  "listenFor": [],
+  "listenFor": null,
   "textHighlights": [],
   "cci_bot_id": "215797fa-5550-4f12-a967-c15437884964",
   "cci_tenant_id": "9f6be790-4a16-4dd6-9850-44a0d2649aef",

src/tests/Microsoft.Agents.Model.Tests/Resources/cps_event_out.json

@@ -1 +1,39 @@
-{"type":"event","id":"470d790f-dcfb-4e7e-9d38-fdae48fcdba0","timestamp":"2024-11-14T03:21:53.5114019\u002B00:00","channelId":"pva-published-engine-direct","from":{"id":"9c73e213-d1a5-edcd-9eee-2db79aadb10f/806d3d4a-5c95-ef11-8a6a-6045bd03ceab","name":"crd17_getsCurrentWeather","role":"bot"},"conversation":{"id":"fe5203d5-03ce-44f1-8fb7-d26bf06ee40f"},"recipient":{"id":"94219457-c13e-44ca-b91c-24078a4997c6","aadObjectId":"94219457-c13e-44ca-b91c-24078a4997c6","role":"user"},"channelData":{"streamType":"final","streamId":"e5084817-2e0d-4fca-bb27-3eca80ae49f8"},"replyToId":"406ffa1e-67a7-4ec9-9eef-f90cfbe0e389","valueType":"DynamicPlanStepBindUpdate","value":{"taskDialogId":"crd17_getsCurrentWeather.topic.MSNWeatherGetcurrentweather","arguments":{"units":"I","Location":"New York"}},"name":"DynamicPlanStepBindUpdate"}
+{
+  "type": "event",
+  "id": "470d790f-dcfb-4e7e-9d38-fdae48fcdba0",
+  "timestamp": "2024-11-14T03:21:53.5114019\u002B00:00",
+  "channelId": "pva-published-engine-direct",
+  "from": {
+    "id": "9c73e213-d1a5-edcd-9eee-2db79aadb10f/806d3d4a-5c95-ef11-8a6a-6045bd03ceab",
+    "name": "crd17_getsCurrentWeather",
+    "role": "bot"
+  },
+  "conversation": { "id": "fe5203d5-03ce-44f1-8fb7-d26bf06ee40f" },
+  "recipient": {
+    "id": "94219457-c13e-44ca-b91c-24078a4997c6",
+    "aadObjectId": "94219457-c13e-44ca-b91c-24078a4997c6",
+    "role": "user"
+  },
+  "membersAdded": [],
+  "membersRemoved": [],
+  "reactionsAdded": [],
+  "reactionsRemoved": [],
+  "attachments": [],
+  "entities": [],
+  "channelData": {
+    "streamType": "final",
+    "streamId": "e5084817-2e0d-4fca-bb27-3eca80ae49f8"
+  },
+  "replyToId": "406ffa1e-67a7-4ec9-9eef-f90cfbe0e389",
+  "valueType": "DynamicPlanStepBindUpdate",
+  "value": {
+    "taskDialogId": "crd17_getsCurrentWeather.topic.MSNWeatherGetcurrentweather",
+    "arguments": {
+      "units": "I",
+      "Location": "New York"
+    }
+  },
+  "name": "DynamicPlanStepBindUpdate",
+  "listenFor": [],
+  "textHighlights": []
+}

src/tests/Microsoft.Agents.Model.Tests/Resources/cps_greeting_out.json

@@ -1 +1,45 @@
-{"type":"message","id":"8a82a3f3-cddf-444b-b607-58c79f3486b8","timestamp":"2024-11-14T03:18:57.5507994\u002B00:00","channelId":"pva-published-engine-direct","from":{"id":"9c73e213-d1a5-edcd-9eee-2db79aadb10f/806d3d4a-5c95-ef11-8a6a-6045bd03ceab","name":"crd17_getsCurrentWeather","role":"bot"},"conversation":{"id":"fe5203d5-03ce-44f1-8fb7-d26bf06ee40f"},"recipient":{"id":"94219457-c13e-44ca-b91c-24078a4997c6","aadObjectId":"94219457-c13e-44ca-b91c-24078a4997c6","role":"user"},"textFormat":"markdown","text":"Hello, I\u0027m Gets Current weather, a virtual assistant. I can answer general questions about the current weather as well as forecasts for today and tomorrow. Just so you are aware, I sometimes use AI to answer your questions.\n\n_**Note**: You can now customize this copilot\u0027s topics and knowledge for your own needs. For more information about this template and how to modify it, visit the template [documentation.](https://go.microsoft.com/fwlink/?linkid=2271069)_","speak":"Thanks for calling, how can I help?","inputHint":"acceptingInput","suggestedActions":{"actions":[{"type":"imBack","title":"What can I ask?","text":"What can I ask?","value":"What can I ask?"}]},"channelData":{"streamType":"final","streamId":"8a82a3f3-cddf-444b-b607-58c79f3486b8"},"replyToId":"b7b28891-a1a4-460d-ad37-11326f46fead"}
+{
+  "type": "message",
+  "id": "8a82a3f3-cddf-444b-b607-58c79f3486b8",
+  "timestamp": "2024-11-14T03:18:57.5507994\u002B00:00",
+  "channelId": "pva-published-engine-direct",
+  "from": {
+    "id": "9c73e213-d1a5-edcd-9eee-2db79aadb10f/806d3d4a-5c95-ef11-8a6a-6045bd03ceab",
+    "name": "crd17_getsCurrentWeather",
+    "role": "bot"
+  },
+  "conversation": { "id": "fe5203d5-03ce-44f1-8fb7-d26bf06ee40f" },
+  "recipient": {
+    "id": "94219457-c13e-44ca-b91c-24078a4997c6",
+    "aadObjectId": "94219457-c13e-44ca-b91c-24078a4997c6",
+    "role": "user"
+  },
+  "textFormat": "markdown",
+  "membersAdded": [],
+  "membersRemoved": [],
+  "reactionsAdded": [],
+  "reactionsRemoved": [],
+  "text": "Hello, I\u0027m Gets Current weather, a virtual assistant. I can answer general questions about the current weather as well as forecasts for today and tomorrow. Just so you are aware, I sometimes use AI to answer your questions.\n\n_**Note**: You can now customize this copilot\u0027s topics and knowledge for your own needs. For more information about this template and how to modify it, visit the template [documentation.](https://go.microsoft.com/fwlink/?linkid=2271069)_",
+  "speak": "Thanks for calling, how can I help?",
+  "inputHint": "acceptingInput",
+  "suggestedActions": {
+    "to": [],
+    "actions": [
+      {
+        "type": "imBack",
+        "title": "What can I ask?",
+        "text": "What can I ask?",
+        "value": "What can I ask?"
+      }
+    ]
+  },
+  "attachments": [],
+  "entities": [],
+  "channelData": {
+    "streamType": "final",
+    "streamId": "8a82a3f3-cddf-444b-b607-58c79f3486b8"
+  },
+  "replyToId": "b7b28891-a1a4-460d-ad37-11326f46fead",
+  "listenFor": [],
+  "textHighlights": []
+}

src/tests/Microsoft.Agents.Model.Tests/Resources/cps_suggestedactions_out.json

@@ -8,18 +8,21 @@
     "name": "crd17_getsCurrentWeather",
     "role": "bot"
   },
-  "conversation": {
-    "id": "fe5203d5-03ce-44f1-8fb7-d26bf06ee40f"
-  },
+  "conversation": { "id": "fe5203d5-03ce-44f1-8fb7-d26bf06ee40f" },
   "recipient": {
     "id": "94219457-c13e-44ca-b91c-24078a4997c6",
     "aadObjectId": "94219457-c13e-44ca-b91c-24078a4997c6",
     "role": "user"
   },
   "textFormat": "markdown",
+  "membersAdded": [],
+  "membersRemoved": [],
+  "reactionsAdded": [],
+  "reactionsRemoved": [],
   "text": "To clarify, did you mean:",
   "inputHint": "acceptingInput",
   "suggestedActions": {
+    "to": [],
     "actions": [
       {
         "type": "imBack",
@@ -47,9 +50,13 @@
       }
     ]
   },
+  "attachments": [],
+  "entities": [],
   "channelData": {
     "streamType": "final",
     "streamId": "80c0db85-7b1e-4a45-a10d-210e7bb0aefd"
   },
-  "replyToId": "40d50db7-7fef-41c2-b804-8346ef266f3d"
+  "replyToId": "40d50db7-7fef-41c2-b804-8346ef266f3d",
+  "listenFor": [],
+  "textHighlights": []
 }

src/tests/Microsoft.Agents.Model.Tests/Resources/cps_typing_out.json

@@ -1,4 +1,12 @@
 {
   "type": "typing",
-  "id": "typing-1"
+  "id": "typing-1",
+  "membersAdded": [],
+  "membersRemoved": [],
+  "reactionsAdded": [],
+  "reactionsRemoved": [],
+  "attachments": [],
+  "entities": [],
+  "listenFor": [],
+  "textHighlights": []
 }