.NET Core
Overview of creating .NET Core functions
The following shows how to get, edit, and pack your template for upload.
Versions | Template |
.NET Core 2.1 |
- After you have downloaded the template project, unzip it and navigate to
./LambdaFunctiondirectory and openLambdaFunction.csprojproject (if you are not using an IDE with automated restore functionality, rundotnet restorein command-line tool inside this folder). - Your entry (main) method will be inside
Function.csfile calledHandler. - After you are done editing your function, open command-line tool inside of
./LambdaFunctiondirectory and rundotnet publish -o lambda. - Navigate to a newly created folder
./lambdaand zip all the contents inside of the directory. - Upload zipped file to CodeMash.
For the handler, you have to specify your entry function location. Handler follows such format -
assembly::namespace.className::methodName. Following the structure given in the initial template, the handler would be LambdaFunction::LambdaFunction.Function::Handler. You can edit any of these parameters for your own function.The following explains how to use provided template to create your own functions.
You define your main function in the handler field. In this case, the main method is
Handler. It takes two parameters - input from CodeMash and function configuration.public async Task<APIGatewayProxyResponse> Handler(CustomEventRequest<BasicInput> lambdaEvent, ILambdaContext context)
{
...
}
CodeMash will always return
CustomEventRequest as an input object. This class takes in generic parameter defining one of the possible input type. The following table explains when to use each of the provided inputs.Class | Description |
BasicInput | Use when executing function through API or using this function in a scheduler task. |
CollectionTriggerInput | Use when using this function as a trigger for collections. |
FileTriggerInput | Use when using this function as a trigger for files. |
UserTriggerInput | Use when using this function as a trigger for users. |
A line below shows how to get the environment variables that you have set up near your function.
var envVariable = Environment.GetEnvironmentVariable("myVariableName");
If you want to user
appsettings.jsonfile the following shows how to read a file. In this case, file is in root directory of a project.public static class AppSettings
{
private static IConfigurationRoot instance;
// Method to get a string from settings
public static string GetString(string key)
{
if (instance == null)
{
// Create an instance with settings
instance = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json")
.Build();
}
// Get value by key
return instance[key];
}
}
Example of a
appsettings.json file:{
"Parameter1": "First parameter.",
"NestedParams": {
"NestedParam1": "First nested parameter."
}
}
Then to get a string from settings:
// First level parameter
var settings = AppSettings.GetString("Parameter1");
// Second level parameter
var nestedSettings = AppSettings.GetString("NestedParams:NestedParam1");
Lambda executor will call your default constructor (without parameters). If you want to add dependency injection to your services, you will have to add a default constructor which calls your wanted constructor.
public class Function
{
private readonly IExampleService _exampleService;
// (Required if adding other constructors. Otherwise, optional.) A default constructor
// called by Lambda. If you are adding your custom constructors,
// default constructor with no parameters must be added
public Function() : this (new ExampleService()) {}
// (Optional) An example of injecting a service. As a default constructor is called by Lambda
// this constructor has to be called from default constructor
public Function(IExampleService exampleService)
{
_exampleService = exampleService;
}
public async Task<APIGatewayProxyResponse> Handler(CustomEventRequest<BasicInput> lambdaEvent, ILambdaContext context)
{
...
// - Call example service
var helloWorldMessage = await _exampleService.GetHelloWorld();
...
}
}
Last modified 2yr ago