If you work with Net Core WebApi project, it already contains the packages for DI, Environment variables. But if you make a console application from the template, it doesn’t contain the packages for environment variables. And if you want to use different configs for Debug and Release, there are 2 ways:

1. remember to write correct ‘appsettings’ file.
2. Use environment variables to automize the process.

I prefer to follow the second step. Further is how to do it.

Add the variable ‘ASPNETCORE_ENVIRONMENT’ and set value ‘Development’ in the properties of the project.

Add code to Program.cs:

var environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
Boolean isDevelopment = environment == "Development";
Console.WriteLine($"isDevelopment: {isDevelopment}");

string configFile = (isDevelopment) ? "appsettings.dev.json" : "appsettings.json";
var configuration = new ConfigurationBuilder()
     .SetBasePath(workDir)
     .AddJsonFile(configFile, optional: true, reloadOnChange: true);

var config = configuration.Build();

Now if you execute the application with Debug mode, 'appsettings.dev.json' will be used, otherwise 'appsettings.json'

Have a nice coding 🙂