AWS Developer Blog

Updates for .NET Core Lambda Libraries

With our release of .NET Core support in AWS Lambda, we also released many NuGet packages to help you develop Lambda functions. We’ve been constantly updating them on our GitHub repository as well. Let’s look at some of the recent updates.


This package contains the integration with the .NET Core CLI, which you can use to deploy your functions. The AWS Toolkit for Visual Studio also uses this package to perform the deployment. For information about this package, see this previous post.

Lambda supports .NET Core 1.0. If you add a dependency to your .NET Core project that requires .NET Core 1.1, the .NET Core publishing tooling used by Amazon.Lambda.Tools will run without errors. However, when you run the function you’ll get errors because of the incompatibility. In version 1.5.0 of Amazon.Lambda.Tools we added validation on top of the .NET Core publishing tool to ensure that none of the dependencies for the project require a later runtime than Lambda supports.

New Events Packages

We have many NuGet packages that contain typed classes modeling the Lambda event types for the services. We recently added two more packages: Amazon.Lambda.LexEvents and Amazon.Lambda.KinesisFirehoseEvents.


Amazon Lex is a service for creating bots. You can use Lambda functions to process the incoming requests to the bot. The Amazon.Lambda.LexEvents package contains the LexEvent and LexResponse classes that you can use as parameter and return for your Lambda functions.

In the Amazon Lex console you can create several getting started Amazon Lex bots. Book Trips is one of the getting started samples you can use to simulate booking a hotel or car. We added a blueprint in Visual Studio that you can use to create the Lambda processor for the Book Trips bot.


Amazon Kinesis Firehose recently added support for using Lambda functions to transform the data being streamed to Amazon S3. The Amazon.Lambda.KinesisFirehoseEvents package contains the KinesisFirehoseEvent and KinesisFirehoseResponse classes. We also added a new getting started blueprint to Visual Studio for Firehose.

Serialization Debugging

As we mentioned, we have many packages providing typed classes that you can use for Lambda functions. You can also define your own classes, and the Amazon.Lambda.Serialization.Json package, which is registered in all of the blueprints we provide, will automatically handle all serializing and deserializing into JSON. In version 1.1.0 of the Amazon.Lambda.Serialization.Json package, we added a new debugging feature to help diagnose serialization issues you might have with your custom types. If you add the environment variable LAMBDA_NET_SERIALIZER_DEBUG with the value of true, the Amazon.Lambda.Serialization.Json package writes the incoming and outgoing JSON to the Amazon CloudWatch log stream. This can be very useful to verify that typed classes are being sent back as you expect.

ASP.NET Core Web API Support

We continue to add features to our ASP.NET Core Web API support on top of Lambda. We are also getting some great support from our community on this project with pull and feature requests. Please keep the feedback coming. In versions 0.10.1-preview1 of Amazon.Lambda.AspNetCoreServer we added:

  • Binary support – see the file for details on how to set this up.
  • Filling in the RemoteIpAddress and RemotePort on HttpContext.Connection from the Amazon API Gateway request.
  • New APIGatewayProxyRequest and ILambdaContext objects for the Lambda function to the HttpContext.Items collection with the collection keys APIGatewayRequest and LambdaContext.

Amazon.Lambda.Templates (1.2.1)

The NuGet package Amazon.Lambda.Templates makes all the blueprints offered in Visual Studio available to the dotnet new command. We recently released version 1.2.1 with the new Amazon Lex and Firehose blueprints, and we updated all the dependencies for the other blueprints. See this earlier blog post on how to install and use the blueprints from the dotnet new command.


We are continually improving our Lambda packages to enhance the experience of developing Lambda functions. Check out the GitHub repo, which is also a great place to give us your feedback. You can also track the releases of the packages in the file.