How to use Dependency Injection in AWS Lambda C# implementation

Question

I have created Lambda functions using AWS.Net SDK, .net core version 1.0. I want to implement dependency injection. Since lambda functions triggered and run independently in AWS environment, there is no such class like Startup present. How and Where can I configure my containers to achieve this implementation?

Answer 1

You can do this. Your FunctionHandler is your entry point to your application.. so you have to wire up the service collection from there.

public class Function
{
    public string FunctionHandler(string input, ILambdaContext context)
    {
        var serviceCollection = new ServiceCollection();
        ConfigureServices(serviceCollection);

        // create service provider
        var serviceProvider = serviceCollection.BuildServiceProvider();

        // entry to run app.
        return serviceProvider.GetService<App>().Run(input);
    }

    private static void ConfigureServices(IServiceCollection serviceCollection)
    {
        // add dependencies here

        // here is where you're adding the actual application logic to the collection
        serviceCollection.AddTransient<App>();
    }
}

public class App
{
    // if you put a constructor here with arguments that are wired up in your services collection, they will be injected.

    public string Run(string input)
    {
        return "This is a test";
    }
}

If you want to wire up logging, have a look here: https://github.com/aws/aws-lambda-dotnet/tree/master/Libraries/src/Amazon.Lambda.Logging.AspNetCore