ASP.NET Core in Azure Functions Custom Handlers

Important: This is a quick proof of concept and how this works is subject to change until custom handlers reaches general availability.

dotnet-react (.NET Core + React app)

This is an ASP.NET Core app built with dotnet new react. There were 3 main changes:

• Program.cs
  • Listen to FUNCTIONS_HTTPWORKER_PORT.
  • Change current working directory to server as the app will run from a subfolder within a function app. This is configured using an app setting named ServerSubfolder.
• Startup.cs
  • Add middleware to rewrite the request path using the __path__ query string.

Build and publish the app

Publish the app into a folder named server in the function app.

cd dotnet-react
dotnet publish -c Release -o ../function-app/server

function-app (main Azure Functions app)

This is the main function app. host.json has been configured to start dotnet server/dotnet-react.dll as the custom hander.

A proxy is configured in proxies.json to forward all requests to /api/index?__path__={path} in the function app. This is currently needed as the original path required for routing in ASP.NET Core is lost when the custom handler is invoked.

There's an index function that invokes the custom handler.

Run locally

func start

Publish to Azure

Create a function app in the Windows consumption plan, then publish with this command:

func azure functionapp publish $FUNCTION_APP_NAME --no-build -b local --force