csharp.md

Getting Started with C#

Prerequisites

• Terraform >= v0.12
• Node.js >= v12.16
• .NET >= Core 3.1

Install CDK for Terraform CLI

Install with Homebrew:

$ brew install cdktf

Or install with npm (comes with Node.js):

npm install -g cdktf-cli

Learn more how to use the cdktf command-line interface here.

Initialize a new CDK for Terraform project

mkdir hello-terraform
cd hello-terraform

Initialize a new CDK for Terraform project

cdktf init --template="csharp" --local

This will initialize a brand new CDK for Terraform project in C# using an interactive command.

Note: By supplying '--local' option you have chosen local storage mode for storing the state of your stack.
This means that your Terraform state file will be stored locally on disk in a file 'terraform.tfstate' in the root of your project.

We will now set up the project. Please enter the details for your project.
If you want to exit, press ^C.

Project Name: (default: 'hello-terraform')
Project Description: (default: 'A simple getting started project for cdktf.')

Also, this command installs the cdktf library so that it can be used in the project.

CDK for Terraform Application

You can now open up the Main.cs file to view your application code.

vim Main.cs

using System;
using Constructs;
using HashiCorp.Cdktf;


namespace MyCompany.MyApp
{
    class MyApp : TerraformStack
    {
        public MyApp(Construct scope, string id) : base(scope, id)
        {
            // define resources here
        }

        public static void Main(string[] args)
        {
            App app = new App();
            new MyApp(app, "hello-terraform");
            app.Synth();
            Console.WriteLine("App synth complete");
        }
    }
}

Refer to the examples directory for additional examples.

Let's take a simple .NET application that uses the CDK for Terraform package.

using System;
using Constructs;
using HashiCorp.Cdktf;

using aws;


namespace MyCompany.MyApp
{
    class MyApp : TerraformStack
    {
        public MyApp(Construct scope, string id) : base(scope, id)
        {
            new AwsProvider(this, "AWS", new AwsProviderConfig {
              Region = "us-east-1"
            });

            new Instance(this, "hello", new InstanceConfig {
              Ami = "ami-2757f631",
              InstanceType = "t2.micro"
            });
        }

        public static void Main(string[] args)
        {
            App app = new App();
            new MyApp(app, "hello-terraform");
            app.Synth();
            Console.WriteLine("App synth complete");
        }
    }
}

Using Terraform Providers

As you can see in the example above we want to deploy AWS resources, therefore we need to use the Terraform AWS Provider. Every Terraform Provider and Terraform Module can be used with the workflow described here.

You specify it in your local cdktf.json file, like this:

{
  "language": "csharp",
  "app": "dotnet run -p MyTerraformStack.csproj",
  "terraformProviders": [
    // Terraform Providers with version constraint go here
    "aws@~> 3.45"
  ],
  "terraformModules": [
    // Terraform Modules with version constraint go here
  ],
  "context": {
    "excludeStackIdFromLogicalIds": "true"
  }
}

Next you need to run cdktf get which generates provider-specific bindings. To save some time you can also use pre-built provider, please visit the "Using Providers and Modules"-Guide for more on that topic.

Synthesize Application

When you are ready you can run the synthesize command to generate Terraform JSON configuration for the application.

cdktf synth

Generated Terraform code in the output directory: cdktf.out

This command will generate a directory called cdktf.out. This directory contains the Terraform JSON configuration for the application.

cd cdktf.out

Terraform AWS provider and instance expressed as Terraform JSON configuration.

cat cdk.json
{
  "terraform": {
    "required_providers": {
      "aws": "~> 2.0"
    }
  },
  "provider": {
    "aws": [
      {
        "region": "us-east-1"
      }
    ]
  },
  "resource": {
    "aws_instance": {
      "hello": {
        "ami": "ami-2757f631",
        "instance_type": "t2.micro"
      }
    }
  }
}

Note: You can generate the Terraform JSON configuration while synthesizing the code by running cdktf synth --json.

Deploy Application

Note: You can use Terraform commands like terraform init, terraform plan, and terraform apply with the generated Terraform JSON configuration (learn more here) or optionally continue to use the CDK for Terraform CLI for a first-class experience.

You can now deploy your CDK for Terraform application using the cdktf deploy command.

cdktf deploy

This command will ask for confirmation on a generated diff and then deploy the application.

Stack: helloterraform
Resources
 + AWS_INSTANCE         hello aws_instance.hello

Diff: 1 to create, 0 to update, 0 to delete.
Do you want to continue (Y/n)? y

Deployed application

Deploying Stack: helloterraform
Resources
 ✔ AWS_INSTANCE         hello aws_instance.hello

Summary: 1 created, 0 updated, 0 destroyed.

The cdktf deploy command runs a terraform apply in the background. If you are using local storage mode then it creates a terraform.tfstate file in the root of the project.

Destroy Application

You can destroy the application by running cdktf destroy.

cdktf destroy

This command will ask for confirmation on a generated diff and then destroy the application if the user confirms that they want to continue with the destroy operation.

Stack: helloterraform
Resources
 - AWS_INSTANCE         hello aws_instance.hello

Diff: 0 to create, 0 to update, 1 to delete.
Do you want to continue (Y/n)?

Destroyed application

Destroying Stack: helloterraform
Resources
 ✔ AWS_INSTANCE         hello aws_instance.hello

Summary: 1 destroyed.