Deploy C# Lambda functions using AWS CDK

Create a project directory for the sample application and navigate into it.

mkdir hello-world
cd hello-world

Initialize a new AWS CDK application by running the following command.

cdk init app --language csharp

The command creates the following files and directories in your project directory

├── README.md
├── cdk.json
└── src
    ├── HelloWorld
    │   ├── GlobalSuppressions.cs
    │   ├── HelloWorld.csproj
    │   ├── HelloWorldStack.cs
    │   └── Program.cs
    └── HelloWorld.sln

Open the src directory and create a new Lambda function using the .NET CLI. This is the function you will deploy using the AWS CDK. In this example, you create a Hello world function named HelloWorldLambdausing the lambda.EmptyFunction template.

cd src
dotnet new lambda.EmptyFunction -n HelloWorldLambda

After this step, your directory structure inside your project directory should look like the following.

├── README.md
├── cdk.json
└── src
    ├── HelloWorld
    │   ├── GlobalSuppressions.cs
    │   ├── HelloWorld.csproj
    │   ├── HelloWorldStack.cs
    │   └── Program.cs
    ├── HelloWorld.sln
    └── HelloWorldLambda
        ├── src
        │   └── HelloWorldLambda
        │       ├── Function.cs
        │       ├── HelloWorldLambda.csproj
        │       ├── Readme.md
        │       └── aws-lambda-tools-defaults.json
        └── test
            └── HelloWorldLambda.Tests
                ├── FunctionTest.cs
                └── HelloWorldLambda.Tests.csproj

Open the HelloWorldStack.cs file from the src/HelloWorld directory. Replace the contents of the file with the following code.

using Amazon.CDK;
using Amazon.CDK.AWS.Lambda;
using Amazon.CDK.AWS.Logs;
using Constructs;

namespace CdkTest
{
    public class HelloWorldStack : Stack
    {
        internal HelloWorldStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
        {
            var buildOption = new BundlingOptions()
            {
                Image = Runtime.DOTNET_8.BundlingImage,
                User = "root",
                OutputType = BundlingOutput.ARCHIVED,
                Command = new string[]{
            "/bin/sh",
                "-c",
                " dotnet tool install -g Amazon.Lambda.Tools"+
                " && dotnet build"+
                " && dotnet lambda package --output-package /asset-output/function.zip"
                }
            };

             var helloWorldLambdaFunction = new Function(this, "HelloWorldFunction", new FunctionProps
            {
                Runtime = Runtime.DOTNET_8,
                MemorySize = 1024,
                LogRetention = RetentionDays.ONE_DAY,
                Handler = "HelloWorldLambda::HelloWorldLambda.Function::FunctionHandler",
                Code = Code.FromAsset("./src/HelloWorldLambda/src/HelloWorldLambda", new Amazon.CDK.AWS.S3.Assets.AssetOptions
                {
                    Bundling = buildOption
                }),
            });
        }
    }
}

This is the code to compile and bundle the application code, as well as the definition of the Lambda function itself. the BundlingOptions object allows a zip file to be created, along with a set of commands that are used to generate the contents of the zip file. In this instance, the dotnet lambda package command is used to compile and generate the zip file.

To deploy your application, run the following command.

cdk deploy

Invoke your deployed Lambda function using the .NET Lambda CLI.

dotnet lambda invoke-function HelloWorldFunction -p "hello world"

After you've finished testing, you can delete the resources you created, unless you want to retain them. Run the following command to delete your resources.

cdk destroy