diff --git a/dotnet/samples/AGENTS.md b/dotnet/samples/AGENTS.md
index 89e1359e857..51059e6cd7e 100644
--- a/dotnet/samples/AGENTS.md
+++ b/dotnet/samples/AGENTS.md
@@ -120,6 +120,10 @@ cd dotnet/samples/01-get-started/01_hello_agent
 dotnet run
 ```
 
+## See also
+
+For implementation conventions and best practices, see [SAMPLE_GUIDELINES.md](./SAMPLE_GUIDELINES.md).
+
 ## Current API notes
 
 - `AIAgent` is the primary agent abstraction (created via `ChatClient.AsAIAgent(...)`)
diff --git a/dotnet/samples/SAMPLE_GUIDELINES.md b/dotnet/samples/SAMPLE_GUIDELINES.md
new file mode 100644
index 00000000000..d15767c17d8
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@@ -0,0 +1,239 @@
+<!-- Copyright (c) Microsoft. All rights reserved. -->
+
+# .NET Samples Guidelines
+
+This document establishes standardized conventions for creating and maintaining samples in the `dotnet/samples/` directory. It complements `AGENTS.md` (which documents structural decisions) with practical guidelines for implementation.
+
+## Environment Variables
+
+All samples use **environment variables** for configuration. Never hardcode credentials, endpoints, or deployment names.
+
+### Foundry Samples Standard
+
+Samples that use Microsoft Foundry must set:
+
+- `FOUNDRY_PROJECT_ENDPOINT` — Your Foundry project endpoint URL
+  - Example: `https://your-foundry-service.services.ai.azure.com/api/projects/your-foundry-project`
+- `FOUNDRY_MODEL` — The model name to use
+  - Example: `gpt-5.4-mini`
+
+### Azure OpenAI Samples
+
+Samples using Azure OpenAI must set:
+
+- `AZURE_OPENAI_ENDPOINT` — Your Azure OpenAI endpoint
+- `AZURE_OPENAI_DEPLOYMENT_NAME` — Your deployment name (defaults to `gpt-5.4-mini` if not set)
+
+### Other Providers
+
+Samples for other providers (OpenAI, Anthropic, Gemini, Ollama, etc.) define their own environment variables in their respective README files.
+
+## Credentials
+
+### DefaultAzureCredential (Recommended)
+
+All canonical samples use `DefaultAzureCredential` from `Azure.Identity`. This credential chain checks multiple credential sources (environment, managed identity, Azure CLI, etc.) and is recommended for production use in Azure environments.
+
+**Important warning**: Always include this comment in sample files using `DefaultAzureCredential`:
+
+```csharp
+// 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.
+```
+
+**For local development**: Run `az login` before running samples to authenticate with Azure CLI.
+
+### Language-Specific Standards
+
+- **.NET samples**: Use `DefaultAzureCredential` (see section above)
+- **Python samples**: Use `AzureCliCredential` (per `python/samples/SAMPLE_GUIDELINES.md`)
+
+## Code Structure
+
+1. **Copyright header** — Start every `.cs` file with:
+   ```csharp
+   // Copyright (c) Microsoft. All rights reserved.
+   ```
+
+2. **Description comment** — Add a brief comment explaining what the sample demonstrates
+
+3. **Using statements** — Group by namespace:
+   - System namespaces first
+   - Azure/Microsoft namespaces next
+   - Project namespaces last
+
+4. **Main code logic** — Keep `Program.cs` focused and linear for readability
+
+5. **Helper methods** — Place at bottom of file
+
+Example structure:
+
+```csharp
+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample demonstrates how to create and run a simple agent with the Foundry service.
+
+using Azure.Identity;
+using Microsoft.Agents.AI;
+
+var endpoint = Environment.GetEnvironmentVariable("FOUNDRY_PROJECT_ENDPOINT")
+    ?? throw new InvalidOperationException("FOUNDRY_PROJECT_ENDPOINT is not set.");
+var model = Environment.GetEnvironmentVariable("FOUNDRY_MODEL") ?? "gpt-5.4-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.
+FoundryAgent agent = new(
+    new Uri(endpoint),
+    new DefaultAzureCredential(),
+    model: model,
+    instructions: "You are a helpful assistant.",
+    name: "MyAgent");
+
+Console.WriteLine(await agent.RunAsync("Hello, tell me about yourself."));
+```
+
+## README Requirements
+
+Every sample must include a `README.md` that documents:
+
+1. **Title** — Clear, concise description of what the sample demonstrates
+
+2. **Overview** — 1–3 sentences explaining the sample's purpose
+
+3. **Prerequisites** — Required tools, environment variables, and setup steps
+   - List required environment variables
+   - For local development: "Run `az login` to authenticate with Azure"
+   - Other tool requirements (e.g., Docker, Node.js)
+
+4. **How to run** — Step-by-step instructions
+   ```bash
+   cd path/to/sample
+   dotnet run
+   ```
+
+5. **Expected output** — Example output or behavior description
+
+6. **Key concepts** — Brief explanation of what the sample teaches
+
+Example README structure:
+
+```markdown
+# My Sample Name
+
+This sample demonstrates [what it demonstrates].
+
+## Prerequisites
+
+- .NET 10 SDK or later
+- Foundry project endpoint and credentials
+- Environment variables:
+  - `FOUNDRY_PROJECT_ENDPOINT` — Your Foundry project endpoint
+  - `FOUNDRY_MODEL` — Model name (e.g., `gpt-5.4-mini`)
+- For local development, run `az login` to authenticate
+
+## How to run
+
+1. Navigate to this directory
+2. Run the sample: `dotnet run`
+
+## Expected output
+
+[Describe what output the user should expect]
+
+## Key concepts
+
+- [Concept 1]: [Brief explanation]
+- [Concept 2]: [Brief explanation]
+```
+
+## Provider Examples
+
+Samples demonstrating specific providers (Azure OpenAI, OpenAI, Anthropic, etc.) should be organized under `02-agents/AgentProviders/[Provider]/` following the pattern:
+
+- `Azure OpenAI/` — Azure OpenAI samples (uses `AzureOpenAIClient`)
+- `OpenAI/` — OpenAI samples (uses `OpenAIClient`)
+- `Anthropic/` — Anthropic samples
+- `Gemini/` — Google Gemini samples
+- `Ollama/` — Ollama local inference samples
+- `Foundry/` — Microsoft Foundry samples (uses `FoundryAgent` or `AIProjectClient`)
+
+Each provider directory contains focused samples demonstrating provider-specific capabilities and API patterns.
+
+## Testing Samples
+
+Use the built-in verification framework in `dotnet/eng/verify-samples/` to ensure all samples build successfully:
+
+```bash
+cd dotnet/eng/verify-samples
+dotnet test
+```
+
+Before committing sample changes:
+
+1. Build the sample locally: `dotnet build`
+2. Run the sample locally (if practical): `dotnet run`
+3. Ensure sample-level build succeeds in CI: `dotnet test` from verify-samples directory
+
+## Common Patterns
+
+### Async/Await
+
+All async methods use the `Async` suffix:
+
+```csharp
+var response = await agent.RunAsync("prompt");
+```
+
+### Error Handling
+
+Use `InvalidOperationException` for missing required configuration:
+
+```csharp
+var endpoint = Environment.GetEnvironmentVariable("FOUNDRY_PROJECT_ENDPOINT")
+    ?? throw new InvalidOperationException("FOUNDRY_PROJECT_ENDPOINT is not set.");
+```
+
+### Agent Instantiation
+
+Prefer the extension method pattern for creating agents:
+
+```csharp
+// Foundry
+FoundryAgent agent = new(
+    new Uri(endpoint),
+    new DefaultAzureCredential(),
+    model: model,
+    instructions: "...",
+    name: "...");
+
+// Alternative: Using AIProjectClient extensions
+AIProjectClient client = new(new Uri(endpoint), new DefaultAzureCredential());
+FoundryAgent agent = client.AsAIAgent(model, instructions, name);
+
+// Azure OpenAI
+AIAgent agent = new AzureOpenAIClient(new Uri(endpoint), new DefaultAzureCredential())
+    .GetChatClient(deploymentName)
+    .AsAIAgent(instructions: "...", name: "...");
+```
+
+### Multi-Turn Conversations
+
+Use `AgentSession` for managing conversation state:
+
+```csharp
+using (AgentSession session = agent.CreateSession())
+{
+    var response1 = await session.SendAsync("First message");
+    var response2 = await session.SendAsync("Follow-up message");
+}
+```
+
+## See Also
+
+- `AGENTS.md` — Structural decisions and design principles
+- `.github/skills/build-and-test/SKILL.md` — Build and test commands
+- `python/samples/SAMPLE_GUIDELINES.md` — Python sample conventions