Using AWSSDK.Extensions.NETCore.Setup and the IConfiguration interface

(This topic was formerly titled, "Configuring the AWS SDK for .NET with .NET Core")

One of the biggest changes in .NET Core is the removal of ConfigurationManager and the standard app.config and web.config files that were used with .NET Framework and ASP.NET applications.

Configuration in .NET Core is based on key-value pairs established by configuration providers. Configuration providers read configuration data into key-value pairs from a variety of configuration sources, including command-line arguments, directory files, environment variables, and settings files.

To make it easy to use the AWS SDK for .NET with .NET Core, you can use the AWSSDK.Extensions.NETCore.Setup NuGet package. Like many .NET Core libraries, it adds extension methods to the IConfiguration interface to make getting the AWS configuration seamless.

Using AWSSDK.Extensions.NETCore.Setup

Suppose that you create an ASP.NET Core Model-View-Controller (MVC) application, which can be accomplished with the ASP.NET Core Web Application template in Visual Studio or by running dotnet new mvc ... in the .NET Core CLI. When you create such an application, the constructor for Startup.cs handles configuration by reading in various input sources from configuration providers such as appsettings.json.

public Startup(IConfiguration configuration)
{
    Configuration = configuration;
}

To use the Configuration object to get the AWS options, first add the AWSSDK.Extensions.NETCore.Setup NuGet package. Then, add your options to the configuration file as described next.

Notice that one of the files added to your project is appsettings.Development.json. This corresponds to an EnvironmentName set to Development. During development, you put your configuration in this file, which is only read during local testing. When you deploy an Amazon EC2 instance that has EnvironmentName set to Production, this file is ignored and the AWS SDK for .NET falls back to the IAM credentials and Region that are configured for the Amazon EC2 instance.

The following configuration settings show examples of the values you can add in the appsettings.Development.json file in your project to supply AWS settings.

{
  "AWS": {
    "Profile": "local-test-profile",
    "Region": "us-west-2"
  },
  "SupportEmail": "TechSupport@example.com"
}

To access a setting in a CSHTML file, use the Configuration directive.

@using Microsoft.Extensions.Configuration
@inject IConfiguration Configuration

<h1>Contact</h1>

<p>
    <strong>Support:</strong> <a href='mailto:@Configuration["SupportEmail"]'>@Configuration["SupportEmail"]</a><br />
</p>

To access the AWS options set in the file from code, call the GetAWSOptions extension method added to IConfiguration.

To construct a service client from these options, call CreateServiceClient. The following example shows how to create an Amazon S3 service client. (Be sure to add the AWSSDK.S3 NuGet package to your project.)

var options = Configuration.GetAWSOptions();
IAmazonS3 client = options.CreateServiceClient<IAmazonS3>();

You can also create multiple service clients with incompatible settings by using multiple entries in the appsettings.Development.json file, as shown in the following examples where the configuration for service1 includes the us-west-2 Region and the configuration for service2 includes the special endpoint URL.

{
  "service1": {
    "Profile": "default",
    "Region": "us-west-2"
  },
  "service2": {
    "Profile": "default",
    "ServiceURL": "URL"
  }
}

You can then get the options for a specific service by using the entry in the JSON file. For example, to get the settings for service1 use the following.

var options = Configuration.GetAWSOptions("service1");

Allowed values in appsettings file

The following app configuration values can be set in the appsettings.Development.json file. The field names must use the casing shown. For details on these settings, see the AWS.Runtime.ClientConfig class.

ASP.NET Core dependency injection

The AWSSDK.Extensions.NETCore.Setup NuGet package also integrates with a new dependency injection system in ASP.NET Core. The ConfigureServices method in your application's Startup class is where the MVC services are added. If the application is using Entity Framework, this is also where that is initialized.

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();
}

The AWSSDK.Extensions.NETCore.Setup NuGet package adds new extension methods to IServiceCollection that you can use to add AWS services to the dependency injection. The following code shows you how to add the AWS options that are read from IConfiguration to add Amazon S3 and DynamoDB to the list of services. (Be sure to add the AWSSDK.S3 and AWSSDK.DynamoDBv2 NuGet packages to your project.)

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();

    services.AddDefaultAWSOptions(Configuration.GetAWSOptions());
    services.AddAWSService<IAmazonS3>();
    services.AddAWSService<IAmazonDynamoDB>();
}

Now, if your MVC controllers use either IAmazonS3 or IAmazonDynamoDB as parameters in their constructors, the dependency injection system passes in those services.

public class HomeController : Controller
{
    IAmazonS3 S3Client { get; set; }

    public HomeController(IAmazonS3 s3Client)
    {
        this.S3Client = s3Client;
    }

    ...

}