AWS Developer Tools Blog

Overriding Endpoints in the AWS SDK for .NET

Sometimes, when sending requests using the AWS SDK for .NET, you are required to explicitly specify an endpoint URL for a service. One such scenario is when you use an older version of the SDK to send requests to a particular service and that service is introduced in a new region. To access the service in the new region without upgrading the SDK, set the ServiceURL property on the client configuration object. Here’s an example with Amazon S3:

var config = new AmazonS3Config { ServiceURL = myUrl };
var s3client = new AmazonS3Client(config);

This technique overrides the default endpoint for a single instance of the service client. It requires code changes to modify the URL for a region, and requires setup everywhere in the code where a service instance is created.

We recently added a feature to the AWS SDK for .NET version 2 ( onwards) that allows developers to specify their own mapping of Service + Regions to URLs, which can vary from environment to environment, keeping the code the same. This default mapping is baked into the SDK, but can be overridden either in the App.config or in code.

To point to the override mapping in your App.config, set the AWSEndpointDefinition appSetting:

   <add key="AWSEndpointDefinition" value="c:pathtoendpoints.xml"

To set the override in code, you can use the AWSConfigs.EndpointDefinition property:

AWSConfigs.EndpointDefinition = @"c:pathtoendpoints.xml";

You can find the most up-to-date version of this file in the Github repository for the SDK. It’s a good idea to start with this file, and then make the needed modifications. It’s also important to note that you need the whole file, not just the endpoints that are different.

When new services and regions are announced, we will update this file along with the SDK.