The appsettings.json file is nothing less than the replacement of the good old Web.config file; the XML syntax has been replaced by a more readable (and less verbose) JSON format. Moreover, the new configuration model is based upon key/value settings that can be retrieved from a wide variety of sources, including--yet not limited to--Json files, using a centralized interface.
Once retrieved, they can be easily accessed within our code using Dependency Injection via literal strings (using the vanilla IConfiguration class):
public SampleController(IConfiguration configuration)
{
var myValue = configuration["Logging:IncludeScopes"];
}
Alternatively, even in a strongly-typed fashion using a custom POCO class (we'll get there later on).
It's worth noting that there's also an appsettings.Development.json file nested below the former one. Such file serves the same purpose of the old Web.Debug.config file since ASP.NET 4.x; everything is written there will override the appsettings.json values as long as the application runs in the development mode.
Back in .NET Core 1.x, this overriding behavior had to be specified manually within the Startup.cs file; in .NET Core 2, the WebHost.CreateDefaultBuilder() method within the Program.cs file takes care of that automatically, assuming that you don't need to add another custom .json configuration file.
Back in .NET Core 1.x, this overriding behavior had to be specified manually within the Startup.cs file; in .NET Core 2, the WebHost.CreateDefaultBuilder() method within the Program.cs file takes care of that automatically, assuming that you don't need to add another custom .json configuration file.
Assuming that we understood everything here, it's time to move on to the next configuration file.