Building a simple .NET REST API with AWS Lambda

This is a very quick demo of how to create a serverless rest API using AWS Lambda and .NET 6. The project is created using the dotnet new command and the Amazon.Lambda.Templates NuGet package.

Installing AWS Lambda Templates

Install the AWS Lambda templates for .NET 6 using the following command:

dotnet new -i Amazon.Lambda.Templates

If already installed check the installed templates using the following command:

dotnet new --list

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

Creating a new project

We will create a new project using the serverless.EmptyServerless template.

dotnet new serverless.EmptyServerless --name SimpleApi --output dotnet-rest-api-with-lambda

Rider IDE

Configuring the project

This project’s purpose is only demostrating how to create a serverless rest API using AWS Lambda and .NET 6.

We don’t need serverless.template file. So, we can delete it.

Now we need to configure aws-lambda-tools-defaults.json file.

We must set function-runtime to dotnet6, function-memory-size to 256 and function-timeout to 30.

function-handler is the name of the class that will handle the request. In this project, we will use SimpleApi::SimpleApi.Functions::Get as the handler.

First part is the assembly name, second part is the namespace and the class name. Last part is the method name.

Looking at the code

We have a Get method in Functions class. This method will handle the request.

public APIGatewayProxyResponse Get(APIGatewayProxyRequest request, ILambdaContext context)
{
    return new APIGatewayProxyResponse
    {
        StatusCode = 200,
        Body = "Hello World!",
        Headers = new Dictionary<string, string> { { "Content-Type", "text/plain" } }
    };
}

Deploying the project

Now that we have created the project, we can deploy it to AWS Lambda. Go to the project directory and run the following command:

dotnet lambda deploy-function

Configuring the Lambda function on AWS Console

We need to configure the Lambda function on AWS Console.

In the Configuration tab, we need to create a new Function URL.

The auth type should be NONE. Then click on Save.

Congratulations!

You have created a serverless rest API using AWS Lambda and .NET 6.