Dotnet Aspire

.NET Aspire Integration Skill

This skill helps add .NET Aspire to existing .NET solutions or create new Aspire-enabled distributed applications. It provides modular guidance for orchestration, service discovery, component integration, configuration management, and deployment.

What Is .NET Aspire?

.NET Aspire is an opinionated, cloud-ready stack for building observable, production-ready, distributed applications. It provides:

• Service orchestration - Coordinate multiple projects and services with dependency management
• Service discovery - Automatic discovery and connection between services
• Telemetry and observability - Built-in logging, metrics, and distributed tracing
• Configuration management - Centralized configuration with strong typing and secrets
• Resource provisioning - Integration with databases, caching, messaging, and cloud services
• Developer dashboard - Local monitoring and debugging interface

When to Use This Skill

Use this skill when:

• Adding Aspire to an existing .NET solution with multiple services
• Creating a new distributed application with Aspire
• Modernizing microservices or distributed systems for cloud deployment
• Setting up service orchestration for local development and deployment
• Integrating cloud-native observability and configuration patterns

What Component/Feature Do I Need?

Overview & Setup

Core Concept

.NET Aspire uses two key projects:

• AppHost - Orchestrates services and resources; provides the developer dashboard
• ServiceDefaults - Shared configuration for all services (OpenTelemetry, health checks, service discovery)

Prerequisites

# Install .NET Aspire workload
dotnet workload install aspire

# Verify installation
dotnet workload list  # Should show "aspire"

# Docker Desktop (for container resources)
# Ensure it's running before launching AppHost

Basic Implementation Flow

1. Analyze the solution

• Identify services (APIs, web apps, workers)
• List external dependencies (databases, Redis, message queues)
• Determine service communication patterns

2. Create Aspire projects

dotnet new aspire-apphost -n MyApp.AppHost
dotnet new aspire-servicedefaults -n MyApp.ServiceDefaults
dotnet sln add MyApp.AppHost/MyApp.AppHost.csproj
dotnet sln add MyApp.ServiceDefaults/MyApp.ServiceDefaults.csproj

3. Configure services

• Add ServiceDefaults reference to each service
• Call builder.AddServiceDefaults() in Program.cs
• Call app.MapDefaultEndpoints() for ASP.NET Core services

4. Orchestrate in AppHost

var builder = DistributedApplication.CreateBuilder(args);

var cache = builder.AddRedis("cache");
var database = builder.AddPostgres("postgres").AddDatabase("appdb");

var api = builder.AddProject<Projects.MyApi>("api")
    .WithReference(database)
    .WithReference(cache);

var web = builder.AddProject<Projects.MyWeb>("web")
    .WithReference(api)
    .WithExternalHttpEndpoints();

builder.Build().Run();

5. Update service communication

• Replace hardcoded URLs with service names
• Use builder.AddServiceDefaults() pattern matching

6. Run and verify

dotnet run --project MyApp.AppHost
# Opens dashboard at https://localhost:15001

Key Decisions

AppHost Project Naming:

• Convention: [SolutionName].AppHost
• Example: For solution "ECommerceSystem", create "ECommerceSystem.AppHost"

Service Resource Names:

• Use short, descriptive names in AppHost
• Examples: "api", "web", "worker", "cache", "database"
• These names are used for service discovery URLs

Resource Management:

• Local development: Use Aspire-managed containers (PostgreSQL, Redis, RabbitMQ)
• Production: Azure resources auto-provisioned by azd or manually configured
• Connection strings: Automatically injected; rarely need hardcoding

Service Discovery Setup:

• HttpClient URLs use service names: http://api instead of https://localhost:7001
• Aspire handles routing and authentication between services
• External services use explicit endpoint configuration

Common Architectures

Web API + Frontend

var api = builder.AddProject<Projects.Api>("api")
    .WithReference(database)
    .WithExternalHttpEndpoints();

var web = builder.AddProject<Projects.Web>("web")
    .WithReference(api)
    .WithExternalHttpEndpoints();

Microservices with Message Queue

var messaging = builder.AddRabbitMQ("messaging");

var orderService = builder.AddProject<Projects.OrderService>("orders")
    .WithReference(messaging);

var inventoryService = builder.AddProject<Projects.InventoryService>("inventory")
    .WithReference(messaging);

Multi-Database System

var postgres = builder.AddPostgres("postgres")
    .AddDatabase("users")
    .AddDatabase("products");

var mongo = builder.AddMongoDB("mongo")
    .AddDatabase("orders");

var userApi = builder.AddProject<Projects.UserApi>("userapi")
    .WithReference(postgres);

var orderApi = builder.AddProject<Projects.OrderApi>("orderapi")
    .WithReference(mongo);

Resource Index

For detailed implementation guidance, see:

• Components - Component packages and integration patterns: resources/components.md
• Service Communication - Service discovery and inter-service calls: resources/service-communication.md
• Configuration Management - Secrets, environment variables, settings: resources/configuration-management.md
• Local Development - Dashboard features, debugging, health checks: resources/local-development.md
• Deployment - Azure Container Apps, Kubernetes, Docker Compose: resources/deployment.md

Best Practices

Service Organization

• Keep AppHost focused on composition, not business logic
• Use ServiceDefaults for cross-cutting concerns (observability, health checks)
• Ensure each service runs independently with fallback configuration

Resource Management

• Use Aspire-managed resources for local development consistency
• Define explicit dependencies in AppHost via .WithReference()
• Add data persistence for databases: .WithDataVolume()

Configuration Patterns

• Development: Use appsettings.Development.json and .WithEnvironment()
• Production: Use Azure Key Vault or managed secrets
• Avoid secrets in source control; use user secrets locally

Observable Services

• Enable OpenTelemetry via ServiceDefaults (automatic)
• Use the developer dashboard for local debugging
• Export telemetry to Application Insights or similar in production

Common Issues & Solutions

Services can't communicate

• Verify service name in AppHost matches HttpClient URL
• Ensure AddServiceDefaults() is called in all services
• Check that ASP.NET services call MapDefaultEndpoints()

Connection strings not injected

• Use builder.AddNpgsqlDbContext<>() instead of manual configuration
• Verify database/resource name matches between AppHost and service
• Confirm ServiceDefaults reference exists in project file

Dashboard won't start

• Ensure Docker Desktop is running
• Check for port conflicts (default: 15001)
• Verify AppHost project runs, not individual services

Health checks failing

• Review resource startup logs in dashboard
• Check port availability on local machine
• Verify Docker has sufficient resources

Getting Started Checklist

• Install .NET Aspire workload and verify
• Analyze solution structure and identify services
• Create AppHost and ServiceDefaults projects
• Add ServiceDefaults reference to each service
• Update service Program.cs with AddServiceDefaults() and MapDefaultEndpoints()
• Configure AppHost orchestration with services and resources
• Update service HttpClient URLs to use service discovery names
• Test locally with dotnet run --project AppHost
• Verify dashboard shows all services running
• Configure deployment target (Azure, Kubernetes, etc.)

Next Steps

1. For component details → See resources/components.md
2. For service communication → See resources/service-communication.md
3. For configuration → See resources/configuration-management.md
4. For local development → See resources/local-development.md
5. For deployment → See resources/deployment.md

Remember: Start with a single service, verify communication works, then add complexity. Use the dashboard to debug issues locally before deploying to production.

1. Which projects should be orchestrated as services?
2. What external resources are needed (databases, Redis, storage, etc.)?
3. Should this use the minimal Aspire setup or include additional components?
4. Are there any existing Docker or orchestration configurations?

2. Clarification Questions

Before implementing, confirm with the user:

Service Identification:

• "I've identified [X] services in your solution: [list]. Should all of these be included in Aspire orchestration?"
• "Are there any additional services or projects that should be added?"

Infrastructure Requirements:

• "I see references to [database/Redis/etc.]. Should Aspire manage these resources?"
• "Do you want to use container resources or connection string configuration?"

Aspire Structure:

• "Should I create a new AppHost project named '[SolutionName].AppHost' and ServiceDefaults project named '[SolutionName].ServiceDefaults'?"
• "Do you prefer a specific naming convention?"

Dependencies:

• "Which services depend on each other? (This helps set up service discovery)"
• "Are there any startup ordering requirements?"

3. Implementation Steps

Step 1: Create Aspire Projects

Create the AppHost project:

dotnet new aspire-apphost -n [SolutionName].AppHost

The AppHost project:

• Orchestrates all services and resources
• Defines service dependencies and configurations
• Provides the developer dashboard for local development
• Contains Program.cs with application composition

Create the ServiceDefaults project:

dotnet new aspire-servicedefaults -n [SolutionName].ServiceDefaults

The ServiceDefaults project:

• Provides shared service configuration
• Configures OpenTelemetry, health checks, and service discovery
• Applied to all services for consistent behavior

Add projects to solution:

dotnet sln add [SolutionName].AppHost/[SolutionName].AppHost.csproj
dotnet sln add [SolutionName].ServiceDefaults/[SolutionName].ServiceDefaults.csproj

Step 2: Configure Service Projects

For each service project (API, Web App, Worker):

1. Add ServiceDefaults reference:

dotnet add [ServiceProject] reference [SolutionName].ServiceDefaults/[SolutionName].ServiceDefaults.csproj

2. Update Program.cs to register service defaults:

// At the top of Program.cs, after builder creation
var builder = WebApplication.CreateBuilder(args);

// Add this line
builder.AddServiceDefaults();

// ... rest of service configuration ...

var app = builder.Build();

// Add this line before app.Run()
app.MapDefaultEndpoints();

app.Run();

3. For Worker Services, the pattern is similar:

var builder = Host.CreateApplicationBuilder(args);

builder.AddServiceDefaults();

// ... service configuration ...

var host = builder.Build();
host.Run();

Step 3: Configure the AppHost

Add project references in AppHost:

dotnet add [SolutionName].AppHost reference [ServiceProject1]/[ServiceProject1].csproj
dotnet add [SolutionName].AppHost reference [ServiceProject2]/[ServiceProject2].csproj

Update AppHost Program.cs to orchestrate services:

var builder = DistributedApplication.CreateBuilder(args);

// Add infrastructure resources
var cache = builder.AddRedis("cache");
var postgres = builder.AddPostgres("postgres")
    .AddDatabase("appdb");

// Add services with dependencies
var apiService = builder.AddProject<Projects.MyApi>("apiservice")
    .WithReference(postgres)
    .WithReference(cache);

var webApp = builder.AddProject<Projects.MyWebApp>("webapp")
    .WithReference(apiService)
    .WithExternalHttpEndpoints();

builder.Build().Run();

Common resource methods:

• .AddRedis("name") - Redis cache
• .AddPostgres("name").AddDatabase("dbname") - PostgreSQL
• .AddSqlServer("name").AddDatabase("dbname") - SQL Server
• .AddRabbitMQ("name") - RabbitMQ messaging
• .AddMongoDB("name").AddDatabase("dbname") - MongoDB
• .AddAzureStorage("name") - Azure Storage

Service configuration methods:

• .WithReference(resource) - Add dependency and inject connection info
• .WithExternalHttpEndpoints() - Make service accessible externally
• .WithReplicas(count) - Run multiple instances
• .WithEnvironment("KEY", "value") - Add environment variables
• .WithHttpsEndpoint(port: 7001) - Specify HTTPS port

Step 4: Add Required NuGet Packages

Aspire packages are automatically added by templates, but verify:

AppHost project:

• Aspire.Hosting.AppHost (typically included via workload)
• Additional hosting packages for resources (e.g., Aspire.Hosting.PostgreSQL)

ServiceDefaults project:

• Microsoft.Extensions.Http.Resilience
• Microsoft.Extensions.ServiceDiscovery
• OpenTelemetry.Exporter.OpenTelemetryProtocol
• OpenTelemetry.Extensions.Hosting
• OpenTelemetry.Instrumentation.AspNetCore
• OpenTelemetry.Instrumentation.Http
• OpenTelemetry.Instrumentation.Runtime

Service projects:

• Aspire.Npgsql.EntityFrameworkCore.PostgreSQL (if using PostgreSQL)
• Aspire.StackExchange.Redis (if using Redis)
• Component packages as needed for databases, messaging, etc.

Install packages:

dotnet add [Project] package [PackageName]

Step 5: Update Service Communication

For services that call other services, use service discovery:

Before (hardcoded URLs):

builder.Services.AddHttpClient("apiservice", client =>
{
    client.BaseAddress = new Uri("https://localhost:7001");
});

After (service discovery):

builder.Services.AddHttpClient("apiservice", client =>
{
    client.BaseAddress = new Uri("http://apiservice");
});

The service name matches the name in AppHost's AddProject<>() call.

For typed HttpClients:

builder.Services.AddHttpClient<IApiClient, ApiClient>(client =>
{
    client.BaseAddress = new Uri("http://apiservice");
});

Step 6: Configuration and Connection Strings

Resource connection strings are automatically injected. Update service configuration:

Before:

builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseNpgsql(builder.Configuration.GetConnectionString("DefaultConnection")));

After:

builder.AddNpgsqlDbContext<AppDbContext>("appdb");

The connection name ("appdb") matches the database name in AppHost.

For Redis:

builder.AddRedisClient("cache");

Step 7: Verify and Test

Run the AppHost project:

dotnet run --project [SolutionName].AppHost

This launches:

• The Aspire dashboard (typically at https://localhost:15001)
• All configured services
• Any resource containers (Redis, PostgreSQL, etc.)

Verify:

1. Dashboard shows all services running
2. Services can communicate via service discovery
3. Telemetry data appears in the dashboard
4. Resource connections work correctly

4. Advanced Configurations

External Services

For services not in the solution:

var externalApi = builder.AddProject<Projects.ExternalApi>("external-api")
    .WithHttpsEndpoint(port: 8001);

Container Resources

Run services in containers:

var myApi = builder.AddContainer("myapi", "myapiimage")
    .WithHttpEndpoint(port: 8000, targetPort: 80);

Azure Resources

For Azure-hosted resources:

var storage = builder.AddAzureStorage("storage")
    .AddBlobs("blobs");

var keyVault = builder.AddAzureKeyVault("keyvault");

Custom Resources

Extend Aspire with custom resources:

var customResource = builder.AddResource(new CustomResource("name"))
    .WithEndpoint("http", endpoint => endpoint.Port = 9000);

Best Practices

1. Service Organization

• Keep AppHost focused on orchestration, not business logic
• Use ServiceDefaults for cross-cutting concerns
• Ensure each service is independently runnable (with fallback config)

2. Resource Management

• Use Aspire-managed resources for local development
• Use connection strings for production deployments
• Configure resource persistence for databases (avoid data loss)

3. Configuration

• Use appsettings.Development.json for local overrides
• Keep sensitive data in user secrets or key vaults
• Use environment-specific configurations

4. Dependencies

• Define explicit service dependencies in AppHost
• Use .WithReference() to inject connection information
• Consider startup order for database migrations

5. Observability

• Leverage built-in OpenTelemetry for distributed tracing
• Use the dashboard for local debugging
• Configure appropriate log levels per service

Common Patterns

API Gateway Pattern

var apiGateway = builder.AddProject<Projects.ApiGateway>("gateway")
    .WithExternalHttpEndpoints();

var serviceA = builder.AddProject<Projects.ServiceA>("servicea");
var serviceB = builder.AddProject<Projects.ServiceB>("serviceb");

apiGateway.WithReference(serviceA).WithReference(serviceB);

Worker with Message Queue

var messaging = builder.AddRabbitMQ("messaging");

var worker = builder.AddProject<Projects.Worker>("worker")
    .WithReference(messaging);

var api = builder.AddProject<Projects.Api>("api")
    .WithReference(messaging);

Web App with Backend API

var cache = builder.AddRedis("cache");
var database = builder.AddPostgres("postgres").AddDatabase("appdb");

var api = builder.AddProject<Projects.Api>("api")
    .WithReference(database)
    .WithReference(cache);

var web = builder.AddProject<Projects.Web>("web")
    .WithReference(api)
    .WithExternalHttpEndpoints();

Troubleshooting

Service Discovery Not Working

• Ensure builder.AddServiceDefaults() is called in service Program.cs
• Verify service name in HttpClient matches AppHost AddProject name
• Check that app.MapDefaultEndpoints() is called for ASP.NET services

Connection Strings Not Injected

• Confirm resource name matches in both AppHost and service configuration
• Use builder.AddNpgsqlDbContext<>() instead of manual AddDbContext
• Verify ServiceDefaults reference exists

Dashboard Not Accessible

• Check AppHost is running (not individual services)
• Verify port isn't blocked (default: 15001)
• Look for dashboard URL in AppHost console output

Resources Not Starting

• Ensure Docker Desktop is running (for container resources)
• Check for port conflicts with existing services
• Review AppHost console for startup errors

Files to Modify

When adding Aspire to an existing solution, expect to modify:

1. Solution file (.sln) - Add AppHost and ServiceDefaults projects
2. Each service's Program.cs - Add service defaults registration
3. Each service's .csproj - Add ServiceDefaults reference
4. AppHost/Program.cs - Define orchestration and resources
5. Service configuration - Replace hardcoded URLs with service discovery
6. Database configuration - Use Aspire component methods

Prerequisites

Ensure the following are installed:

• .NET 8.0 SDK or later
• .NET Aspire workload: dotnet workload install aspire
• Docker Desktop (for container resources)

Verify installation:

dotnet workload list

Should show "aspire" in the installed workloads.

Summary Checklist

After implementing Aspire, verify:

• AppHost project created and added to solution
• ServiceDefaults project created and added to solution
• All service projects reference ServiceDefaults
• Service Program.cs files call AddServiceDefaults() and MapDefaultEndpoints()
• AppHost Program.cs orchestrates all services with proper dependencies
• Service-to-service communication uses service discovery (not hardcoded URLs)
• Database and cache connections use Aspire component methods
• AppHost runs successfully and launches dashboard
• All services appear in dashboard and show healthy status
• Telemetry data appears for requests across services

Additional Resources

For detailed information about specific components and patterns, see:

• resources/components.md - Aspire component packages and configurations
• resources/deployment.md - Deploying Aspire applications to production

Example Output

When complete, the solution structure should look like:

MySolution/
├── MySolution.sln
├── MySolution.AppHost/
│   ├── Program.cs                 # Orchestration configuration
│   ├── MySolution.AppHost.csproj
│   └── appsettings.json
├── MySolution.ServiceDefaults/
│   ├── Extensions.cs              # Service defaults implementation
│   └── MySolution.ServiceDefaults.csproj
├── MySolution.Api/
│   ├── Program.cs                 # Calls AddServiceDefaults()
│   └── MySolution.Api.csproj      # References ServiceDefaults
├── MySolution.Web/
│   ├── Program.cs                 # Calls AddServiceDefaults()
│   └── MySolution.Web.csproj      # References ServiceDefaults
└── MySolution.Worker/
    ├── Program.cs                 # Calls AddServiceDefaults()
    └── MySolution.Worker.csproj   # References ServiceDefaults

Running dotnet run --project MySolution.AppHost starts all services and opens the dashboard for monitoring and debugging the distributed application.