Dotnet Core 使用哪个 appsettings.json 文件作为默认环境或父文件？

Question

What dictates which .json file the .net core clr / runtime uses? For example if there's a connection string in both. I can't find an answer anywhere.

var env = builderContext.HostingEnvironment;
                config.AddJsonFile("appsettings.json", optional: false)
                      .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true);

Thanks!

Answer 1

There's no "default" order. .NET Core will use the files specified in your code. There's nothing special about appsettings.json or the Json configuration provider either. As far as .NET Core is concerned they just providers

This code specifies that :

1. The required appsettings.json file is loaded first. If it doesn't exist the app fails
2. The optional environment-specific file is loaded next, which may override the first one. If it doesn't exist, nothing is loaded

Even the expression $"appsettings.{env.EnvironmentName}.json" has no special meaning. It's a string interpolation expression that replaces the {env.EnvironmentName} placeholder with the value of the env.EnvironmentName property.

The method call error specifies the order, with later files or providers overriding earlier ones.

You could add a command-line or EF Core provider after the JSON files to override them with values stored in the database or specified in the command line.

This is explained in the documentation and tutorials, eg Configuration in ASP.NET Core or the Essential .NET - Configuration in .NET Core but it's so different from how the Full framework works that it takes a bit of getting used to.

Answer 2

Config is loaded in source-order. In other words, each type of config you specify is loaded in the order you add it in your Startup.cs or whatever. Here, since appsettings.json is specified before appsettings.{env.EnvironmentName}.json , it will be loaded first, followed by the environment-specific version, if it exists.

No matter your config sources, everything ends up in the ConfigurationRoot dictionary. If multiple config sources specify the same key, then the last one in wins. In other words, config sources added later override those added earlier.