How do you add a configuration file to a .NET Core console application?

Question

When I create a .NET Core console application, an appsettings.json file is not included like it is with an ASP.NET Core application.

Answer 1

Typically, the configuration is injected into the constructor of a class. However, with console applications, dependency injection is not configured by default. So we need to add a few lines of code to accomplish this.

1. First we need to add the Microsoft.Extensions.Hosting NuGet package.
2. Add the appsettings.json file. NOTE: it must be named this exactly.
3. Add the following code to the Main procedure of the Program.cs file:

var host = Host.CreateDefaultBuilder()
    .ConfigureServices((context, services) => { 
        services.AddTransient<IDoSomethingService, DoSomethingService>(); 
    })
    .Build();

var svc = ActivatorUtilities.CreateInstance<DoSomethingService>(host.Services);

svc.Generate();

4. You'll need the following using statements:

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;

5. Create your class (and possibly interface) that will contain your application code. Make sure you inject the configuration into the constructor.

class DoSomethingService : IDoSomethingService
{

    private IConfiguration _config;

    public DoSomethingService(IConfiguration config)
    {
        _config = config;
    }

    public void Generate()
    {
        System.Console.WriteLine("Generate is running.");
        System.Console.WriteLine(_config.GetConnectionString("Test"));
    }

}

6. In this example, we are storing a connection string in the appsettings.json file like so:

{
  "ConnectionStrings": {
    "Test": "TEST_CONNECTION_STRING"
  }
}