# 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