This project shows how to run an ASP.NET Core Web API project as an AWS Lambda exposed through Amazon API Gateway. The NuGet package Amazon.Lambda.AspNetCoreServer contains a Lambda function that is used to translate requests from API Gateway into the ASP.NET Core framework and then the responses from ASP.NET Core back to API Gateway.

The project starts with two Web API controllers. The first is the example ValuesController that is created by default for new ASP.NET Core Web API projects. The second is S3ProxyController which uses the AWS SDK for .NET to proxy requests for an Amazon S3 bucket.

To integrate the AWS SDK for .NET with the dependency injection system built into ASP.NET Core the NuGet package AWSSDK.Extensions.NETCore.Setup is referenced. In the Startup.cs file the Amazon S3 client is added to the dependency injection framework. The S3ProxyController will get its S3 service client from there.

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    // Add S3 to the ASP.NET Core dependency injection framework.
    services.AddAWSService<Amazon.S3.IAmazonS3>();
}

To configure this project to handle requests from an Application Load Balancer instead of API Gateway change the base class of LambdaEntryPoint from Amazon.Lambda.AspNetCoreServer.APIGatewayProxyFunction to Amazon.Lambda.AspNetCoreServer.ApplicationLoadBalancerFunction.

• serverless.template - an AWS CloudFormation Serverless Application Model template file for declaring your Serverless functions and other AWS resources
• aws-lambda-tools-defaults.json - default argument settings for use with Visual Studio and command line deployment tools for AWS
• LambdaEntryPoint.cs - class that derives from Amazon.Lambda.AspNetCoreServer.APIGatewayProxyFunction. The code in this file bootstraps the ASP.NET Core hosting framework. The Lambda function is defined in the base class. Change the base class to Amazon.Lambda.AspNetCoreServer.ApplicationLoadBalancerFunction when using an Application Load Balancer.
• LocalEntryPoint.cs - for local development this contains the executable Main function which bootstraps the ASP.NET Core hosting framework with Kestrel, as for typical ASP.NET Core applications.
• Startup.cs - usual ASP.NET Core Startup class used to configure the services ASP.NET Core will use.
• web.config - used for local development.
• Controllers\S3ProxyController - Web API controller for proxying an S3 bucket
• Controllers\ValuesController - example Web API controller

You may also have a test project depending on the options selected.

To deploy your Serverless application, right click the project in Solution Explorer and select Publish to AWS Lambda.

To view your deployed application open the Stack View window by double-clicking the stack name shown beneath the AWS CloudFormation node in the AWS Explorer tree. The Stack View also displays the root URL to your published application.

Once you have edited your template and code you can deploy your application using the Amazon.Lambda.Tools Global Tool from the command line.

Install Amazon.Lambda.Tools Global Tools if not already installed.

    dotnet tool install -g Amazon.Lambda.Tools

If already installed check if new version is available.

    dotnet tool update -g Amazon.Lambda.Tools

Execute unit tests

    cd "Country.Api.Serverless/test/Country.Api.Serverless.Tests"
    dotnet test

Deploy application

    cd "Country.Api.Serverless/src/Country.Api.Serverless"
    dotnet lambda deploy-serverless