# Developing with AWS Step Functions using .NET Core

## Requirements

The Serverless Application Model Command Line Interface (SAM CLI) is an extension of the AWS CLI that adds functionality for building and testing Lambda applications. It uses Docker to run your functions in an Amazon Linux environment that matches Lambda.

To use the SAM CLI, you need the following tools:

* [AWS CLI](https://aws.amazon.com/cli/) configured with Administrator permission
* SAM CLI - [Install the SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html)
* .NET Core - [Install .NET Core](https://www.microsoft.com/net/download)
* Docker - [Install Docker community edition](https://hub.docker.com/search/?type=edition&offering=community)

Please see the [currently supported patch of each major version of .NET Core](https://github.com/aws/aws-lambda-dotnet#version-status) to ensure your functions are compatible with the AWS Lambda runtime.

## Building your application

To build and deploy your application for the first time, run the following in your shell:

```bash
sam build
sam deploy --guided
```

The first command will build the source of your application. The second command will package and deploy your application to AWS, with a series of prompts:

* **Stack Name**: The name of the stack to deploy to CloudFormation. This should be unique to your account and region, and a good starting point would be something matching your project name.
* **AWS Region**: The AWS region you want to deploy your app to.
* **Confirm changes before deploy**: If set to yes, any change sets will be shown to you before execution for manual review. If set to no, the AWS SAM CLI will automatically deploy application changes.
* **Allow SAM CLI IAM role creation**: Many AWS SAM templates, including this example, create AWS IAM roles required for the AWS Lambda function(s) included to access AWS services. By default, these are scoped down to minimum required permissions. To deploy an AWS CloudFormation stack which creates or modified IAM roles, the `CAPABILITY_IAM` value for `capabilities` must be provided. If permission isn't provided through this prompt, to deploy this example you must explicitly pass `--capabilities CAPABILITY_IAM` to the `sam deploy` command.
* **Save arguments to samconfig.toml**: If set to yes, your choices will be saved to a configuration file inside the project, so that in the future you can just re-run `sam deploy` without parameters to deploy changes to your application.

You can find your API Gateway Endpoint URL in the output values displayed after deployment.

## Use the SAM CLI to build and test locally

Build the Lambda functions in your application with the `sam build` command.

```bash
plagiarism-demo$ sam build
```

The SAM CLI installs dependencies defined in `functions/FunctionName.csproj`, creates a deployment package, and saves it in the `.aws-sam/build` folder.

## Add a resource to your application

The application template uses AWS Serverless Application Model (AWS SAM) to define application resources. AWS SAM is an extension of AWS CloudFormation with a simpler syntax for configuring common serverless application resources such as functions, triggers, and APIs. For resources not included in [the SAM specification](https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md), you can use standard [AWS CloudFormation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html) resource types.

## Fetch, tail, and filter Lambda function logs

To simplify troubleshooting, SAM CLI has a command called `sam logs`. `sam logs` lets you fetch logs generated by your deployed Lambda function from the command line. In addition to printing the logs on the terminal, this command has several nifty features to help you quickly find the bug.

`NOTE`: This command works for all AWS Lambda functions; not just the ones you deploy using SAM.

```bash
plagiarism-demo$ sam logs -n RegisterIncidentFunction --stack-name plagiarism-demo --tail
```

You can find more information and examples about filtering Lambda function logs in the [SAM CLI Documentation](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-logging.html).

## Cleanup

To delete the sample application that you created, use the AWS CLI. Assuming you used your project name for the stack name, you can run the following:

```bash
aws cloudformation delete-stack --stack-name plagiarism-demo
```

## Resources

See the [AWS SAM developer guide](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/what-is-sam.html) for an introduction to SAM specification, the SAM CLI, and serverless application concepts.

Next, you can use AWS Serverless Application Repository to deploy ready to use Apps that go beyond hello world samples and learn how authors developed their applications: [AWS Serverless Application Repository main page](https://aws.amazon.com/serverless/serverlessrepo/)

## Next Steps

Create your own .NET Core solution template to use with SAM CLI. [Cookiecutter for AWS SAM and .NET](https://github.com/aws-samples/cookiecutter-aws-sam-dotnet) provides you with a sample implementation how to use cookiecutter templating library to standardise how you initialise your Serverless projects.

``` bash
 sam init --location gh:aws-samples/cookiecutter-aws-sam-dotnet
```

For more information and examples of how to use `sam init` run 

``` bash
sam init --help
```