.NET: Add Code Interpreter container file download samples

dotnet/agent-framework-dotnet.slnx

@@ -152,6 +152,7 @@
     <Project Path="samples/02-agents/AgentsWithFoundry/Agent_Step21_WebSearch/Agent_Step21_WebSearch.csproj" />
     <Project Path="samples/02-agents/AgentsWithFoundry/Agent_Step22_MemorySearch/Agent_Step22_MemorySearch.csproj" />
     <Project Path="samples/02-agents/AgentsWithFoundry/Agent_Step23_LocalMCP/Agent_Step23_LocalMCP.csproj" />
+    <Project Path="samples/02-agents/AgentsWithFoundry/Agent_Step24_CodeInterpreterFileDownload/Agent_Step24_CodeInterpreterFileDownload.csproj" />
   </Folder>
   <Folder Name="/Samples/02-agents/AgentWithMemory/">
     <File Path="samples/02-agents/AgentWithMemory/README.md" />
@@ -167,6 +168,7 @@
     <Project Path="samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step03_CreateFromChatClient/Agent_OpenAI_Step03_CreateFromChatClient.csproj" />
     <Project Path="samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step04_CreateFromOpenAIResponseClient/Agent_OpenAI_Step04_CreateFromOpenAIResponseClient.csproj" />
     <Project Path="samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step05_Conversation/Agent_OpenAI_Step05_Conversation.csproj" />
+    <Project Path="samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step06_CodeInterpreterFileDownload/Agent_OpenAI_Step06_CodeInterpreterFileDownload.csproj" />
   </Folder>
   <Folder Name="/Samples/02-agents/AgentWithRAG/">
     <File Path="samples/02-agents/AgentWithRAG/README.md" />

dotnet/samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step06_CodeInterpreterFileDownload/Agent_OpenAI_Step06_CodeInterpreterFileDownload.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.OpenAI\Microsoft.Agents.AI.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step06_CodeInterpreterFileDownload/Program.cs

@@ -0,0 +1,98 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample shows how to download files generated by Code Interpreter using the Containers API.
+// Code Interpreter generates files inside containers (cfile_ / cntr_ IDs) which cannot be
+// downloaded via the standard Files API. Use ContainerClient instead.
+
+#pragma warning disable OPENAI001
+
+using System.ClientModel;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+using OpenAI;
+using OpenAI.Containers;
+using OpenAI.Responses;
+
+string apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? throw new InvalidOperationException("OPENAI_API_KEY is not set.");
+string model = Environment.GetEnvironmentVariable("OPENAI_CHAT_MODEL_NAME") ?? "gpt-4o-mini";
+
+var openAIClient = new OpenAIClient(new ApiKeyCredential(apiKey));
+
+// Create an agent with Code Interpreter tool enabled
+AIAgent agent = openAIClient
+    .GetResponsesClient()
+    .AsAIAgent(
+        model: model,
+        instructions: "You are a helpful assistant that can generate files using code.",
+        name: "CodeInterpreterAgent",
+        tools: [new HostedCodeInterpreterTool()]);
+
+// Ask the agent to generate a file
+AgentResponse response = await agent.RunAsync(
+    "Create a CSV file with the multiplication times tables from 1 to 12. Include headers.");
+
+// Display the text response
+foreach (ChatMessage message in response.Messages)
+{
+    foreach (AIContent content in message.Contents)
+    {
+        if (content is TextContent textContent)
+        {
+            Console.WriteLine(textContent.Text);
+        }
+    }
+}
+
+// Extract container file citations from response annotations and download
+ContainerClient containerClient = openAIClient.GetContainerClient();
+
+HashSet<string> downloadedFiles = [];
+bool foundContainerFiles = false;
+
+foreach (ChatMessage message in response.Messages)
+{
+    foreach (AIContent content in message.Contents)
+    {
+        if (content.Annotations is null)
+        {
+            continue;
+        }
+
+        foreach (AIAnnotation annotation in content.Annotations)
+        {
+            // Container files from Code Interpreter have ContainerFileCitationMessageAnnotation as raw representation
+            if (annotation is CitationAnnotation citation
+                && citation.RawRepresentation is ContainerFileCitationMessageAnnotation containerCitation)
+            {
+                foundContainerFiles = true;
+
+                // Deduplicate by container+file ID in case the same file is cited multiple times
+                string key = $"{containerCitation.ContainerId}/{containerCitation.FileId}";
+                if (!downloadedFiles.Add(key))
+                {
+                    continue;
+                }
+
+                Console.WriteLine($"\nDownloading container file: {containerCitation.Filename}");
+                Console.WriteLine($"  Container ID: {containerCitation.ContainerId}");
+                Console.WriteLine($"  File ID:      {containerCitation.FileId}");
+
+                BinaryData fileData = await containerClient.DownloadContainerFileAsync(
+                    containerCitation.ContainerId,
+                    containerCitation.FileId);
+
+                // Sanitize filename to prevent path traversal
+                string safeFilename = Path.GetFileName(containerCitation.Filename);
+                string outputPath = Path.Combine(Directory.GetCurrentDirectory(), safeFilename);
+                await File.WriteAllBytesAsync(outputPath, fileData.ToArray());
+                Console.WriteLine($"  Saved to:     {outputPath}");
+            }
+        }
+    }
+}
+
+if (!foundContainerFiles)
+{
+    Console.WriteLine("\nNo container file citations found in the response.");
+    Console.WriteLine("The model may not have generated a downloadable file for this prompt.");
+}

dotnet/samples/02-agents/AgentWithOpenAI/Agent_OpenAI_Step06_CodeInterpreterFileDownload/README.md

@@ -0,0 +1,51 @@
+# Code Interpreter File Download (OpenAI)
+
+This sample demonstrates how to download files generated by Code Interpreter when using the OpenAI Responses API.
+
+## What this sample demonstrates
+
+- Creating an agent with Code Interpreter tool using `ResponsesClient.AsAIAgent()`
+- Generating files through Code Interpreter (e.g., CSV, Excel, images)
+- Extracting container file citations from agent response annotations
+- Downloading container files using the `ContainerClient` API
+
+## Container files vs regular files
+
+When Code Interpreter generates a file, the file is stored inside a **container** with a `cntr_` prefixed ID. The file itself gets a `cfile_` prefixed ID.
+
+These container files **cannot** be downloaded using the standard Files API (`GetOpenAIFileClient`), which returns 404 for `cfile_` IDs. Instead, you must use the **Containers API** (`GetContainerClient`) to download them:
+
+```csharp
+// ❌ This does NOT work for container files
+var filesClient = openAIClient.GetOpenAIFileClient();
+await filesClient.DownloadFileAsync("cfile_...");  // Returns 404
+
+// ✅ Use ContainerClient instead
+var containerClient = openAIClient.GetContainerClient();
+await containerClient.DownloadContainerFileAsync("cntr_...", "cfile_...");
+```
+
+The container ID and file ID are available from the `ContainerFileCitationMessageAnnotation` annotation in the response, accessible via `CitationAnnotation.RawRepresentation`.
+
+## Prerequisites
+
+- .NET 10 SDK or later
+- OpenAI API key with access to a model that supports Code Interpreter
+
+Set the following environment variables:
+
+```powershell
+$env:OPENAI_API_KEY="sk-..."
+$env:OPENAI_CHAT_MODEL_NAME="gpt-4o-mini"  # Optional, defaults to gpt-4o-mini
+```
+
+## Run the sample
+
+```powershell
+dotnet run
+```
+
+## See also
+
+- [Code Interpreter File Download with Foundry](../../../02-agents/AgentsWithFoundry/Agent_Step24_CodeInterpreterFileDownload/) — same scenario using Microsoft Foundry
+- [Code Interpreter](../../../02-agents/AgentsWithFoundry/Agent_Step14_CodeInterpreter/) — Code Interpreter without file download

dotnet/samples/02-agents/AgentWithOpenAI/README.md

@@ -14,4 +14,5 @@ Agent Framework provides additional support to allow OpenAI developers to use th
 |[Using Reasoning Capabilities](./Agent_OpenAI_Step02_Reasoning/)|This sample demonstrates how to create an AI agent with reasoning capabilities using OpenAI's reasoning models and response types.|
 |[Creating an Agent from a ChatClient](./Agent_OpenAI_Step03_CreateFromChatClient/)|This sample demonstrates how to create an AI agent directly from an OpenAI.Chat.ChatClient instance using OpenAIChatClientAgent.|
 |[Creating an Agent from an OpenAIResponseClient](./Agent_OpenAI_Step04_CreateFromOpenAIResponseClient/)|This sample demonstrates how to create an AI agent directly from an OpenAI.Responses.OpenAIResponseClient instance using OpenAIResponseClientAgent.|
-|[Managing Conversation State](./Agent_OpenAI_Step05_Conversation/)|This sample demonstrates how to maintain conversation state across multiple turns using the AgentSession for context continuity.|
+|[Managing Conversation State](./Agent_OpenAI_Step05_Conversation/)|This sample demonstrates how to maintain conversation state across multiple turns using the AgentSession for context continuity.|
+|[Code Interpreter File Download](./Agent_OpenAI_Step06_CodeInterpreterFileDownload/)|This sample demonstrates how to download files generated by Code Interpreter using the Containers API (`cfile_`/`cntr_` IDs).|

dotnet/samples/02-agents/AgentsWithFoundry/Agent_Step24_CodeInterpreterFileDownload/Agent_Step24_CodeInterpreterFileDownload.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Identity" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.Foundry\Microsoft.Agents.AI.Foundry.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/02-agents/AgentsWithFoundry/Agent_Step24_CodeInterpreterFileDownload/Program.cs

@@ -0,0 +1,100 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample shows how to download files generated by Code Interpreter using Microsoft Foundry.
+// Code Interpreter generates files inside containers (cfile_ / cntr_ IDs) which cannot be
+// downloaded via the standard Files API. Use ContainerClient from the project's OpenAI client instead.
+
+#pragma warning disable OPENAI001
+
+using Azure.AI.Projects;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+using OpenAI.Responses;
+
+string endpoint = Environment.GetEnvironmentVariable("AZURE_AI_PROJECT_ENDPOINT") ?? throw new InvalidOperationException("AZURE_AI_PROJECT_ENDPOINT is not set.");
+string deploymentName = Environment.GetEnvironmentVariable("AZURE_AI_MODEL_DEPLOYMENT_NAME") ?? "gpt-4o-mini";
+
+// WARNING: DefaultAzureCredential is convenient for development but requires careful consideration in production.
+// In production, consider using a specific credential (e.g., ManagedIdentityCredential) to avoid
+// latency issues, unintended credential probing, and potential security risks from fallback mechanisms.
+AIProjectClient aiProjectClient = new(new Uri(endpoint), new DefaultAzureCredential());
+
+// Create an agent with Code Interpreter tool enabled
+AIAgent agent = aiProjectClient.AsAIAgent(
+    deploymentName,
+    instructions: "You are a helpful assistant that can generate files using code.",
+    name: "CodeInterpreterAgent",
+    tools: [new HostedCodeInterpreterTool()]);
+
+// Ask the agent to generate a file
+AgentResponse response = await agent.RunAsync(
+    "Create a CSV file with the multiplication times tables from 1 to 12. Include headers.");
+
+// Display the text response
+foreach (ChatMessage message in response.Messages)
+{
+    foreach (AIContent content in message.Contents)
+    {
+        if (content is TextContent textContent)
+        {
+            Console.WriteLine(textContent.Text);
+        }
+    }
+}
+
+// Extract container file citations from response annotations and download.
+// AIProjectClient.GetProjectOpenAIClient() returns a ProjectOpenAIClient (inherits from OpenAI.OpenAIClient)
+// which supports GetContainerClient(), unlike AzureOpenAIClient which does not.
+var containerClient = aiProjectClient.GetProjectOpenAIClient().GetContainerClient();
+
+HashSet<string> downloadedFiles = [];
+bool foundContainerFiles = false;
+
+foreach (ChatMessage message in response.Messages)
+{
+    foreach (AIContent content in message.Contents)
+    {
+        if (content.Annotations is null)
+        {
+            continue;
+        }
+
+        foreach (AIAnnotation annotation in content.Annotations)
+        {
+            // Container files from Code Interpreter have ContainerFileCitationMessageAnnotation as raw representation
+            if (annotation is CitationAnnotation citation
+                && citation.RawRepresentation is ContainerFileCitationMessageAnnotation containerCitation)
+            {
+                foundContainerFiles = true;
+
+                // Deduplicate by container+file ID in case the same file is cited multiple times
+                string key = $"{containerCitation.ContainerId}/{containerCitation.FileId}";
+                if (!downloadedFiles.Add(key))
+                {
+                    continue;
+                }
+
+                Console.WriteLine($"\nDownloading container file: {containerCitation.Filename}");
+                Console.WriteLine($"  Container ID: {containerCitation.ContainerId}");
+                Console.WriteLine($"  File ID:      {containerCitation.FileId}");
+
+                BinaryData fileData = await containerClient.DownloadContainerFileAsync(
+                    containerCitation.ContainerId,
+                    containerCitation.FileId);
+
+                // Sanitize filename to prevent path traversal
+                string safeFilename = Path.GetFileName(containerCitation.Filename);
+                string outputPath = Path.Combine(Directory.GetCurrentDirectory(), safeFilename);
+                await File.WriteAllBytesAsync(outputPath, fileData.ToArray());
+                Console.WriteLine($"  Saved to:     {outputPath}");
+            }
+        }
+    }
+}
+
+if (!foundContainerFiles)
+{
+    Console.WriteLine("\nNo container file citations found in the response.");
+    Console.WriteLine("The model may not have generated a downloadable file for this prompt.");
+}

dotnet/samples/02-agents/AgentsWithFoundry/Agent_Step24_CodeInterpreterFileDownload/README.md

@@ -0,0 +1,56 @@
+# Code Interpreter File Download (Microsoft Foundry)
+
+This sample demonstrates how to download files generated by Code Interpreter when using Microsoft Foundry.
+
+## What this sample demonstrates
+
+- Creating an agent with Code Interpreter tool using `AIProjectClient.AsAIAgent()`
+- Generating files through Code Interpreter (e.g., CSV, Excel, images)
+- Extracting container file citations from agent response annotations
+- Downloading container files using the `ContainerClient` via `AIProjectClient.GetProjectOpenAIClient()`
+
+## Container files vs regular files
+
+When Code Interpreter generates a file, the file is stored inside a **container** with a `cntr_` prefixed ID. The file itself gets a `cfile_` prefixed ID.
+
+These container files **cannot** be downloaded using the standard Files API (`GetOpenAIFileClient`), which returns 404 for `cfile_` IDs. Instead, you must use the **Containers API** to download them.
+
+### Getting the ContainerClient with Foundry
+
+`AzureOpenAIClient.GetContainerClient()` is not supported and throws `InvalidOperationException`. Instead, use the project's OpenAI client which inherits directly from `OpenAI.OpenAIClient`:
+
+```csharp
+// ❌ AzureOpenAIClient does not support ContainerClient
+var azureClient = new AzureOpenAIClient(endpoint, credential);
+azureClient.GetContainerClient();  // Throws InvalidOperationException
+
+// ✅ Use AIProjectClient's project OpenAI client
+var containerClient = aiProjectClient.GetProjectOpenAIClient().GetContainerClient();
+await containerClient.DownloadContainerFileAsync("cntr_...", "cfile_...");
+```
+
+The container ID and file ID are available from the `ContainerFileCitationMessageAnnotation` annotation in the response, accessible via `CitationAnnotation.RawRepresentation`.
+
+## Prerequisites
+
+- .NET 10 SDK or later
+- Microsoft Foundry service endpoint and deployment configured
+- Azure CLI installed and authenticated (`az login`)
+
+Set the following environment variables:
+
+```powershell
+$env:AZURE_AI_PROJECT_ENDPOINT="https://your-foundry-service.services.ai.azure.com/api/projects/your-foundry-project"
+$env:AZURE_AI_MODEL_DEPLOYMENT_NAME="gpt-4o-mini"  # Optional, defaults to gpt-4o-mini
+```
+
+## Run the sample
+
+```powershell
+dotnet run
+```
+
+## See also
+
+- [Code Interpreter File Download with OpenAI](../../../02-agents/AgentWithOpenAI/Agent_OpenAI_Step06_CodeInterpreterFileDownload/) — same scenario using Public OpenAI
+- [Code Interpreter](../Agent_Step14_CodeInterpreter/) — Code Interpreter without file download

dotnet/samples/02-agents/AgentsWithFoundry/README.md

@@ -72,6 +72,7 @@ Some samples require extra tool-specific environment variables. See each sample
 | [Web search](./Agent_Step21_WebSearch/) | Web search tool |
 | [Memory search](./Agent_Step22_MemorySearch/) | Memory search tool |
 | [Local MCP](./Agent_Step23_LocalMCP/) | Local MCP client with HTTP transport |
+| [Code interpreter file download](./Agent_Step24_CodeInterpreterFileDownload/) | Download container files generated by code interpreter |
 
 ## Running the samples