README.md

ASP.NET Core Web API Integration

Demonstrates integrating Replane into an ASP.NET Core Web API with:

• Dependency injection
• Feature flags middleware
• Per-request context evaluation

Prerequisites

• .NET 8.0 SDK or later
• A running Replane server
• An SDK key from your Replane project

Setup

1. Copy this directory to your local machine:

   cp -r WebApiIntegration ~/my-replane-example
   cd ~/my-replane-example

2. Set your environment variables:

   export REPLANE_BASE_URL="https://your-replane-server.com"
   export REPLANE_SDK_KEY="your-sdk-key"

   Or use appsettings.json:

   {
     "Replane": {
       "BaseUrl": "https://your-replane-server.com",
       "SdkKey": "your-sdk-key"
     }
   }

3. Restore packages:

   dotnet restore

Running

dotnet run

The API will start at http://localhost:5000 (or the port shown in console).

Open Swagger UI at: http://localhost:5000/swagger

API Endpoints

GET /

Returns the welcome message from config.

curl http://localhost:5000/
# {"message":"Welcome to the API!"}

GET /health

Health check endpoint (bypasses maintenance mode).

curl http://localhost:5000/health
# {"status":"healthy"}

GET /config/{name}

Get a specific config value.

curl http://localhost:5000/config/api-rate-limit
# {"name":"api-rate-limit","value":100}

GET /features

Get user-specific features based on context from headers.

# Free user
curl http://localhost:5000/features \
  -H "X-User-Id: user-123" \
  -H "X-User-Plan: free"
# {"userId":"user-123","plan":"free","features":{"premiumFeatureEnabled":false,"rateLimit":100}}

# Premium user
curl http://localhost:5000/features \
  -H "X-User-Id: user-456" \
  -H "X-User-Plan: premium"
# {"userId":"user-456","plan":"premium","features":{"premiumFeatureEnabled":true,"rateLimit":1000}}

What This Example Demonstrates

Singleton Registration

Register the Replane client as a singleton service:

builder.Services.AddSingleton(replaneClient);

Startup Connection

Connect to Replane during app startup:

try
{
    await replaneClient.ConnectAsync();
}
catch (ReplaneException ex)
{
    // Fall back to default values
}

Middleware Integration

Use Replane for middleware decisions:

app.Use(async (context, next) =>
{
    var client = context.RequestServices.GetRequiredService<ReplaneClient>();
    var maintenanceMode = client.Get<bool>("maintenance-mode");

    if (maintenanceMode)
    {
        context.Response.StatusCode = 503;
        return;
    }

    await next();
});

Per-Request Context

Build context from request headers/JWT:

app.MapGet("/features", (HttpContext http, ReplaneClient client) =>
{
    var context = new ReplaneContext
    {
        ["user_id"] = http.Request.Headers["X-User-Id"].FirstOrDefault(),
        ["plan"] = http.Request.Headers["X-User-Plan"].FirstOrDefault()
    };

    return client.Get<bool>("premium-feature", context);
});

Graceful Shutdown

Dispose the client on shutdown:

lifetime.ApplicationStopping.Register(() =>
{
    replaneClient.Dispose();
});

Best Practices

1. Register as singleton - The client maintains a persistent connection
2. Connect at startup - Don't connect on first request
3. Handle connection failures - Use defaults for resilience
4. Build context from request - User ID, plan, region from JWT/headers
5. Dispose on shutdown - Clean up the SSE connection

Common Patterns

Feature Flags

if (client.Get<bool>("new-search-enabled", userContext))
{
    return await NewSearchAsync();
}
return await OldSearchAsync();

Rate Limiting

var rateLimit = client.Get<int>("api-rate-limit", userContext);
// Apply rate limit

A/B Testing

var variant = client.Get<string>("checkout-flow", userContext);
// "variant-a" or "variant-b" based on user segmentation