Is there an alternate to Web.config Transormations in Asp.NET Core appsettings.json? - deployment

Question

Is there an alternate to Web.config Transormations in Asp.NET Core appsettings.json?
I would like to change connection strings and other settins when deploying to staging.production server from VS.

Answer 1

First of all, keep in mind, that
ASP.NET Core’s configuration system has been re-architected from previous versions of ASP.NET, which relied on System.Configuration and XML configuration files like web.config. The new configuration model provides streamlined access to key/value based settings that can be retrieved from a variety of sources.
To work with settings in your ASP.NET application, it is recommended that you only instantiate a Configuration in your application’s Startup class. At its simplest, Configuration is just a collection of sources, which provide the ability to read and write name/value pairs.
ASP.NET Core provides built-in support for JSON, XML, and INI configuration files as sources and allows to choose source accordinly to current environment. The ASPNETCORE_ENVIRONMENT environment variable is used to setup/determine the current environment. Predefined values are Development, Staging, Production, but can be any custom also.
Lets say you want to use JSON file (named appsettings.json for convention) for storing connection string. What you need to do is to create a separate appsettings.{EnvironmentName}.json files (for each environment you have) like:
appsettings.Development.json
appsettings.Staging.json
appsettings.Production.json
and load one of them accordingly to environment:
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true);
Read more about all of this in the “Configuration” chapter and the “Working with multiple environments” chapter of the ASP.NET Core documentation.

Answer 2

Yes, you must use environment variables on the target system.
ASP.NET Core references a particular environment variable, ASPNETCORE_ENVIRONMENT to describe the environment the application is currently running in. This variable can be set to any value you like, but three values are used by convention: Development, Staging, and Production. You will find these values used in the samples and templates provided with ASP.NET Core.
Determining the environment at runtime
The IHostingEnvironment service provides the core abstraction for working with environments. This service is provided by the ASP.NET hosting layer, and can be injected into your startup logic via Dependency Injection. The ASP.NET Core web site template in Visual Studio uses this approach to load environment-specific configuration files (if present) and to customize the app’s error handling settings. In both cases, this behavior is achieved by referring to the currently specified environment by calling EnvironmentName or IsEnvironment on the instance of IHostingEnvironment passed into the appropriate method.
https://docs.asp.net/en/latest/fundamentals/environments.html