Twia.AzureFunction.SimpleInjector

This project provides a NuGet package to support the use of Simple Injector to inject dependencies as bindings into an Azure Function.

Latest baster branch build: and Release:

Introduction

This package is based on the nice start given by Boris Wilhelms in his blog Dependency injection for Azure Function v2. This has been used to specialize it for Simple Injector and also simplify its usage.

Get the package

The package is available on NuGet with ID Twia.AzureFunction.SimpleInjector.

Usage

In short:

Create a class derived from IStartup and implement void Build(Container container).
Register this class in the WebJobsStartupAttribute using SimpleInjectorStartup<T>, where T is this previously created class.
If access to IWebJobsBuilder builder is required, then extend the class with implementation of the IConfigureFunction interface.

Using the default configuration

The following example code shows how to configure the dependency injection, using the default configuration for logging:

using System.IO;
using Microsoft.Extensions.Configuration;
using Microsoft.Azure.WebJobs.Hosting;
using SimpleInjector;
using Twia.AzureFunction.SimpleInjector;

// Register the Startup class as the entry point for the extension.
[assembly: WebJobsStartup(typeof(SimpleInjectorStartup<Startup, >))]

/// <summary>
/// This class takes care of registering the SimpleInjector bindings required by this Function App.
/// </summary>
internal class Startup : IStartup
{
    /// <summary>
    /// Build the Simple Injector Container.
    /// </summary>
    /// <param name="container">The container in which to register all dependencies.</param>
    public void Build(Container container)
    {
        container.RegisterInstance(BuildConfiguration());
        container.RegisterSingleton<IExampleService, ExampleService>();
    }

    /// <summary>
    ///  Add support for the use of configuration in services.
    /// </summary>
    /// <returns>An instance of <see cref="IConfiguration"/>.</returns>
    private static IConfiguration BuildConfiguration()
    {
        return new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("local.settings.json", optional: true, reloadOnChange: false)
                .AddEnvironmentVariables()
                .Build();
    }
}

Using your own configuration

A configuration class can be provided that defines which support for logging must be added. By default support for ILogger is addded, but through this configuration also support for ILogger<T> can be added.

The configuration class can be implemented according to the following example:

using Twia.AzureFunction.SimpleInjector;

public class StartupConfiguration : IStartConfiguration
{
    public bool AddILogger => true;

    public bool AddILoggerOfT => true;
}

Then change the line

[assembly: WebJobsStartup(typeof(SimpleInjectorStartup<Startup>))]

[assembly: WebJobsStartup(typeof(SimpleInjectorStartup<Startup, StartupConfiguration>))]

to use the custom configuration.

Access to the IWebJobsBuilder builder

To get access to the IWebJobsBuilder builder, to configure the function before SimpleInjector is configured, the following steps can be taken:

Extend the startup class with IConfigureFunction:

internal class Startup : IStartup, IConfigureFunction

And implement the interface in the Startup class. For example:

    public void ConfigureFunction(IWebJobsBuilder builder)
    {
        builder.Services.AddHttpClient();
    }