01 - Run Locally (Premium)¶

Build and run a .NET 8 isolated worker Function App locally before touching Azure resources.

Prerequisites¶

Tool	Version	Purpose
.NET SDK	8.0 (LTS)	Build and run isolated worker functions
Azure Functions Core Tools	v4	Start local host and publish artifacts
Azure CLI	2.61+	Provision Azure resources and inspect app state

Premium plan basics

Premium (EP1) keeps at least one warm instance, supports VNet integration, private endpoints, and deployment slots. No cold-start penalty, with up to 100 instances and no execution timeout.

What You'll Build¶

A .NET 8 isolated worker Function App with 16 functions that runs locally, returning JSON from /api/health, and validates the isolated hosting model before deployment.

flowchart LR
    A[dotnet build] --> B[func start]
    B --> C[HTTP Trigger endpoint]
    C --> D[HttpRequest via ASP.NET Core]
    D --> E[IActionResult response]

Steps¶

Step 1 - Clone and navigate to the reference app¶

cd apps/dotnet

Step 2 - Review the project structure¶

apps/dotnet/
├── Functions/
│   ├── HealthFunction.cs
│   ├── HelloHttpFunction.cs
│   ├── InfoFunction.cs
│   ├── LogLevelsFunction.cs
│   ├── SlowResponseFunction.cs
│   ├── TestErrorFunction.cs
│   ├── UnhandledErrorFunction.cs
│   ├── DnsResolveFunction.cs
│   ├── IdentityProbeFunction.cs
│   ├── StorageProbeFunction.cs
│   ├── ExternalDependencyFunction.cs
│   ├── QueueProcessorFunction.cs
│   ├── BlobProcessorFunction.cs
│   ├── ScheduledCleanupFunction.cs
│   ├── TimerLabFunction.cs
│   └── EventHubLagProcessorFunction.cs
├── Shared/
│   └── AppConfig.cs
├── Program.cs
├── host.json
├── local.settings.json.example
└── AzureFunctionsGuide.csproj

Step 3 - Configure local settings¶

cp local.settings.json.example local.settings.json

Verify the file contains:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "QueueStorage": "UseDevelopmentStorage=true",
    "EventHubConnection": "Endpoint=sb://placeholder.servicebus.windows.net/;SharedAccessKeyName=placeholder;SharedAccessKey=cGxhY2Vob2xkZXI=;EntityPath=events"
  }
}

Step 4 - Review Program.cs for isolated hosting¶

using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .Build();

host.Run();

Isolated worker model

The .NET isolated worker uses ConfigureFunctionsWebApplication() with ASP.NET Core integration. HTTP functions use HttpRequest and IActionResult from ASP.NET Core, and logging is constructor-injected with ILogger<T>.

Step 5 - Build and start the function host¶

dotnet build
func start

Step 6 - Test the health endpoint¶

In a second terminal:

curl --request GET "http://localhost:7071/api/health"

Expected response:

{"status":"healthy","timestamp":"2026-04-10T03:24:15.123Z","version":"1.0.0"}

Test additional endpoints:

curl --request GET "http://localhost:7071/api/hello/World"
curl --request GET "http://localhost:7071/api/info"

Verification¶

Azure Functions Core Tools
Core Tools Version:       4.8.0
Function Runtime Version: 4.x.x.x

Functions:

        blobProcessor: blobTrigger

        dnsResolve: [GET] http://localhost:7071/api/dns/{hostname}

        eventhubLagProcessor: eventHubTrigger

        externalDependency: [GET] http://localhost:7071/api/dependency

        health: [GET] http://localhost:7071/api/health

        helloHttp: [GET] http://localhost:7071/api/hello/{name?}

        identityProbe: [GET] http://localhost:7071/api/identity

        info: [GET] http://localhost:7071/api/info

        logLevels: [GET] http://localhost:7071/api/loglevels

        queueProcessor: queueTrigger

        scheduledCleanup: timerTrigger

        slowResponse: [GET] http://localhost:7071/api/slow

        storageProbe: [GET] http://localhost:7071/api/storage/probe

        testError: [GET] http://localhost:7071/api/testerror

        timerLab: timerTrigger

        unhandledError: [GET] http://localhost:7071/api/unhandlederror

Next Steps¶

Next: 02 - First Deploy