# Building AWS Lambda Functions with .NET 6 [Serverless computing](https://aws.amazon.com/serverless/) has gained popularity in the last few years primarily because it allows a true platform-as-a-service environment, letting developers focus on coding rather than back-end operations. Under this context, [AWS Lambda](https://docs.aws.amazon.com/lambda/latest/dg/welcome.html) is one of the best alternatives to start using this hosting model for our .NET 6 applications. ### Prerequisites - Have a [IAM User](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_users_create.html#id_users_create_console) with programmatic access. - Setup your [AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html) locally. ### Tools Install the Amazon Lambda Templates: ```powershell dotnet new -i Amazon.Lambda.Templates ``` Now we can see the list of AWS Lambda Templates installed running this command `dotnet new --list --tag lambda`: ```powershell Template Name Short Name Language Tags ---------------------------------------------------- -------------------------------------------- -------- --------------------- Empty Top-level Function lambda.EmptyTopLevelFunction [C#] AWS/Lambda/Serverless Lambda Annotations Framework (Preview) serverless.Annotations [C#] AWS/Lambda/Serverless Lambda ASP.NET Core Minimal API serverless.AspNetCoreMinimalAPI [C#] AWS/Lambda/Serverless Lambda ASP.NET Core Web API serverless.AspNetCoreWebAPI [C#],F# AWS/Lambda/Serverless Lambda ASP.NET Core Web API (.NET 6 Container Image) serverless.image.AspNetCoreWebAPI [C#],F# AWS/Lambda/Serverless Lambda ASP.NET Core Web Application with Razor Pages serverless.AspNetCoreWebApp [C#] AWS/Lambda/Serverless Lambda Custom Runtime Function (.NET 6) lambda.CustomRuntimeFunction [C#],F# AWS/Lambda/Function Lambda Detect Image Labels lambda.DetectImageLabels [C#],F# AWS/Lambda/Function Lambda Empty Function lambda.EmptyFunction [C#],F# AWS/Lambda/Function Lambda Empty Function (.NET 6 Container Image) lambda.image.EmptyFunction [C#],F# AWS/Lambda/Function Lambda Empty Serverless serverless.EmptyServerless [C#],F# AWS/Lambda/Serverless Lambda Empty Serverless (.NET 6 Container Image) serverless.image.EmptyServerless [C#],F# AWS/Lambda/Serverless Lambda Giraffe Web App serverless.Giraffe F# AWS/Lambda/Serverless Lambda Simple Application Load Balancer Function lambda.SimpleApplicationLoadBalancerFunction [C#] AWS/Lambda/Function Lambda Simple DynamoDB Function lambda.DynamoDB [C#],F# AWS/Lambda/Function Lambda Simple Kinesis Firehose Function lambda.KinesisFirehose [C#] AWS/Lambda/Function Lambda Simple Kinesis Function lambda.Kinesis [C#],F# AWS/Lambda/Function Lambda Simple S3 Function lambda.S3 [C#],F# AWS/Lambda/Function Lambda Simple SNS Function lambda.SNS [C#] AWS/Lambda/Function Lambda Simple SQS Function lambda.SQS [C#] AWS/Lambda/Function Lex Book Trip Sample lambda.LexBookTripSample [C#] AWS/Lambda/Function Order Flowers Chatbot Tutorial lambda.OrderFlowersChatbot [C#] AWS/Lambda/Function Serverless Detect Image Labels serverless.DetectImageLabels [C#],F# AWS/Lambda/Serverless Serverless Simple S3 Function serverless.S3 [C#],F# AWS/Lambda/Serverless Serverless WebSocket API serverless.WebSocketAPI [C#] AWS/Lambda/Serverless Step Functions Hello World serverless.StepFunctionsHelloWorld [C#],F# AWS/Lambda/Serverless ``` We can install the [AWS Toolkit for Visual Studio](https://docs.aws.amazon.com/lambda/latest/dg/csharp-package-toolkit.html) to have the same templates installed. Install the [Amazon Lambda Tools](https://github.com/aws/aws-lambda-dotnet): ```powershell dotnet tool install -g Amazon.Lambda.Tools ``` ### Simple HTTP API Run the following commands to create the project and solution: ```powershell dotnet new lambda.EmptyFunction -n SimpleHTTPAPI -o . dotnet new sln -n aws-lambda-sandbox dotnet sln add --in-root src/SimpleHTTPAPI ``` Open the solution in your Visual Studio and add the following Nuget package to the project: - [Amazon.Lambda.APIGatewayEvents](https://www.nuget.org/packages/Amazon.Lambda.APIGatewayEvents/2.4.1) Modify the `Function.cs` file as follows: ```csharp using Amazon.Lambda.APIGatewayEvents; using Amazon.Lambda.Core; using System.Net; using System.Text.Json; [assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))] namespace SimpleHTTPAPI; public class Function { public APIGatewayProxyResponse FunctionHandler(APIGatewayProxyRequest request, ILambdaContext context) { context.Logger.LogInformation("Request: " + JsonSerializer.Serialize(request)); var response = new APIGatewayProxyResponse { StatusCode = (int)HttpStatusCode.OK, Body = "Hello World", Headers = new Dictionary { { "Content-Type", "text/plain" } } }; return response; } } ``` Edit the original 'aws-lambda-tools-defaults.json' file to have: ```json { "Information": [ "This file provides default values for the deployment wizard inside Visual Studio and the AWS Lambda commands added to the .NET Core CLI.", "To learn more about the Lambda commands with the .NET Core CLI execute the following command at the command line in the project root directory.", "dotnet lambda help", "All the command line options for the Lambda command can be specified in this file." ], "profile": "[profile]", "region": "[region]", "configuration": "Release", "function-runtime": "dotnet6", "function-memory-size": 256, "function-timeout": 30, "function-handler": "SimpleHTTPAPI::SimpleHTTPAPI.Function::FunctionHandler", "function-url-enable": true, "function-name": "SimpleHTTPAPI" } ``` - [region] is the AWS Region where we will create the Lambda. An Example of a region is `us-east-2`. - [profile], usually is `default` and was defined at the moment to set up your AWS CLI. At this point, we can test the application using the `Mock Lambda Test Tool` profile included in the project. ![Mock.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1657380455475/n0trik7pY.PNG align="left") Time to deploy, run the following command: ```powershell dotnet lambda deploy-function --project-location src/SimpleHTTPAPI ``` You will be asked which IAM role you want to use, select the `*** Create new IAM Role ***` option, and enter a name for the IAM Role. Finally, you will be asked what permissions to grant, select `AWSLambdaBasicExecutionRole`. And that's it, your Lambda is up and running in AWS: ![lambdasimplehttpapi.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1657384734988/FuwryFijL.png align="left") Open the `Function URL` to see the response of the endpoint. ### ASP.NET Core Web API Now let's see how easy it is to deploy an ASP.NET Core Web API: ```powershell dotnet new webapi -n ASPNETCoreWebAPI dotnet sln add ASPNETCoreWebAPI ``` Add the following Nuget package: - [Amazon.Lambda.AspNetCoreServer.Hosting](https://www.nuget.org/packages/Amazon.Lambda.AspNetCoreServer.Hosting/1.3.0) Modify the `Program.cs` file as follows: ```csharp var builder = WebApplication.CreateBuilder(args); // Add services to the container. builder.Services.AddControllers(); // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle builder.Services.AddEndpointsApiExplorer(); builder.Services.AddSwaggerGen(); builder.Services.AddAWSLambdaHosting(LambdaEventSource.HttpApi); var app = builder.Build(); app.UseSwagger(); app.UseSwaggerUI(); app.UseHttpsRedirection(); app.UseAuthorization(); app.MapControllers(); app.Run(); ``` And add the `aws-lambda-tools-defaults.json` file with the following content: ```json { "Information": [ "This file provides default values for the deployment wizard inside Visual Studio and the AWS Lambda commands added to the .NET Core CLI.", "To learn more about the Lambda commands with the .NET Core CLI execute the following command at the command line in the project root directory.", "dotnet lambda help", "All the command line options for the Lambda command can be specified in this file." ], "profile": "[profile]", "region": "[region]", "configuration": "Release", "function-runtime": "dotnet6", "function-memory-size": 256, "function-timeout": 30, "function-handler": "ASPNETCoreWebAPI", "function-url-enable": true } ``` Run the command to start the deployment and follow the steps of the previous example to complete it: ```powershell dotnet lambda deploy-function --project-location ASPNETCoreWebAPI ``` ![lambdaapi.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1657388067548/xSwY3mrnN.png align="left") Open the `Function URL` to see the Swagger page of the API: ![swagger.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1657388166117/05ssPd5ni.PNG align="left") All the code is available [here](https://github.com/raulnq/aws-lambda-sandbox). Thanks and happy coding.