.Net: Ignore unknown response item types rather than throw (#12596)

### Motivation and Context

Closes #12511 

### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

Author: markwallace-microsoft

dotnet/samples/GettingStartedWithAgents/OpenAIResponse/Step03_OpenAIResponseAgent_ReasoningModel.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft. All rights reserved.
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.Agents.OpenAI;
+
+namespace GettingStarted.OpenAIResponseAgents;
+
+/// <summary>
+/// This example demonstrates using <see cref="OpenAIResponseAgent"/>.
+/// </summary>
+public class Step03_OpenAIResponseAgent_ReasoningModel(ITestOutputHelper output) : BaseResponsesAgentTest(output, "o4-mini")
+{
+    [Fact]
+    public async Task UseOpenAIResponseAgentWithAReasoningModelAsync()
+    {
+        // Define the agent
+        OpenAIResponseAgent agent = new(this.Client)
+        {
+            Name = "ResponseAgent",
+            Instructions = "Answer all queries with a detailed response.",
+        };
+
+        // Invoke the agent and output the response
+        var responseItems = agent.InvokeAsync("Which of the last four Olympic host cities has the highest average temperature?");
+        await foreach (ChatMessageContent responseItem in responseItems)
+        {
+            WriteAgentChatMessage(responseItem);
+        }
+    }
+}

dotnet/src/Agents/OpenAI/Extensions/OpenAIResponseExtensions.cs

@@ -43,7 +43,7 @@ public static ChatMessageContent ToChatMessageContent(this OpenAIResponse respon
     /// </summary>
     /// <param name="item">The response item to convert.</param>
     /// <returns>A <see cref="ChatMessageContent"/> instance.</returns>
-    public static ChatMessageContent ToChatMessageContent(this ResponseItem item)
+    public static ChatMessageContent? ToChatMessageContent(this ResponseItem item)
     {
         if (item is MessageResponseItem messageResponseItem)
         {
@@ -54,7 +54,7 @@ public static ChatMessageContent ToChatMessageContent(this ResponseItem item)
         {
             return new ChatMessageContent(AuthorRole.Assistant, item.ToChatMessageContentItemCollection(), innerContent: functionCallResponseItem);
         }
-        throw new NotSupportedException($"Unsupported response item: {item.GetType()}");
+        return null;
     }
 
     /// <summary>
@@ -92,7 +92,7 @@ public static ChatMessageContentItemCollection ToChatMessageContentItemCollectio
             };
             return [functionCallContent];
         }
-        throw new NotImplementedException($"Unsupported response item: {item.GetType()}");
+        return [];
     }
 
     /// <summary>

dotnet/src/Agents/OpenAI/OpenAIResponseAgentThread.cs

@@ -111,7 +111,11 @@ public async IAsyncEnumerable<ChatMessageContent> GetMessagesAsync([EnumeratorCa
             var collectionResult = this._client.GetResponseInputItemsAsync(this.ResponseId, default, cancellationToken).ConfigureAwait(false);
             await foreach (var responseItem in collectionResult)
             {
-                yield return responseItem.ToChatMessageContent();
+                var messageContent = responseItem.ToChatMessageContent();
+                if (messageContent is not null)
+                {
+                    yield return messageContent;
+                }
             }
         }
     }

dotnet/src/Agents/UnitTests/Extensions/ResponseItemExtensionsTests.cs

@@ -35,7 +35,8 @@ public void VerifyToChatMessageContentFromInputText(string creationMethod, strin
         // Act  
         var messageContent = responseItem.ToChatMessageContent();
 
-        // Assert  
+        // Assert
+        Assert.NotNull(messageContent);
         Assert.Equal(new AuthorRole(roleLabel), messageContent.Role);
         Assert.Single(messageContent.Items);
         Assert.IsType<TextContent>(messageContent.Items[0]);
@@ -53,6 +54,7 @@ public void VerifyToChatMessageContentFromInputImage()
         var messageContent = responseItem.ToChatMessageContent();
 
         // Assert
+        Assert.NotNull(messageContent);
         Assert.Equal(AuthorRole.User, messageContent.Role);
         Assert.Single(messageContent.Items);
         Assert.IsType<FileReferenceContent>(messageContent.Items[0]);
@@ -71,6 +73,7 @@ public void VerifyToChatMessageContentFromInputFile()
         var messageContent = responseItem.ToChatMessageContent();
 
         // Assert
+        Assert.NotNull(messageContent);
         Assert.Equal(AuthorRole.User, messageContent.Role);
         Assert.Single(messageContent.Items);
         Assert.IsType<BinaryContent>(messageContent.Items[0]);
@@ -88,9 +91,24 @@ public void VerifyToChatMessageContentFromRefusal()
         var messageContent = responseItem.ToChatMessageContent();
 
         // Assert
+        Assert.NotNull(messageContent);
         Assert.Equal(AuthorRole.User, messageContent.Role);
         Assert.Single(messageContent.Items);
         Assert.IsType<TextContent>(messageContent.Items[0]);
         Assert.Equal("refusal", ((TextContent)messageContent.Items[0]).Text);
     }
+
+    [Fact]
+    public void VerifyToChatMessageContentFromReasoning()
+    {
+        // Arrange
+        IEnumerable<string> summaryParts = ["Foo"];
+        ReasoningResponseItem responseItem = ResponseItem.CreateReasoningItem(summaryParts);
+
+        // Act
+        var messageContent = responseItem.ToChatMessageContent();
+
+        // Assert
+        Assert.Null(messageContent);
+    }
 }

dotnet/src/Agents/UnitTests/OpenAI/Extensions/OpenAIResponseExtensionsTests.cs

@@ -50,8 +50,8 @@ public void VerifyToChatMessageContentWithResponseItem()
         ResponseItem functionCall = ResponseItem.CreateFunctionCallItem("callId", "functionName", new BinaryData("{}"));
 
         // Act
-        ChatMessageContent userMessageContent = userMessage.ToChatMessageContent();
-        ChatMessageContent functionCallContent = functionCall.ToChatMessageContent();
+        ChatMessageContent? userMessageContent = userMessage.ToChatMessageContent();
+        ChatMessageContent? functionCallContent = functionCall.ToChatMessageContent();
 
         // Assert
         Assert.NotNull(userMessageContent);

dotnet/src/InternalUtilities/samples/AgentUtilities/BaseResponsesAgentTest.cs

@@ -11,7 +11,7 @@
 /// </summary>
 public abstract class BaseResponsesAgentTest : BaseAgentsTest<OpenAIResponseClient>
 {
-    protected BaseResponsesAgentTest(ITestOutputHelper output) : base(output)
+    protected BaseResponsesAgentTest(ITestOutputHelper output, string? model = null) : base(output)
     {
         var options = new OpenAIClientOptions();
         if (this.EnableLogging)
@@ -25,7 +25,7 @@ protected BaseResponsesAgentTest(ITestOutputHelper output) : base(output)
             });
         }
 
-        this.Client = new(model: TestConfiguration.OpenAI.ModelId, credential: new ApiKeyCredential(TestConfiguration.OpenAI.ApiKey), options: options);
+        this.Client = new(model: model ?? TestConfiguration.OpenAI.ModelId, credential: new ApiKeyCredential(TestConfiguration.OpenAI.ApiKey), options: options);
     }
 
     protected bool EnableLogging { get; set; } = false;