Access from class library to appsetting.json in Asp.net-core

Question

I am trying to access appsetting.json file from a class library. So far the solution that I found is to create a configuration class implementing interface IConfiguration from Microsoft.Extensions.Configuration and add the json file to class and read from the same.

var configuration = new Configuration();
configuration.AddJsonFile("appsetting.json");
var connectionString= configuration.Get("connectionString");

This seems to be bad option as we have to add the json file each time we have to access the appsetting configuration. Dont we have any alternative like ConfigurationManager in ASP.NET.

Answer 1

I'm assuming you want to access the appsettings.json file from the web application since class libraries don't have an appsettings.json by default.

I create a model class that has properties that match the settings in a section in appsettings.json.

Section in appsettings.json

"ApplicationSettings": {
    "SmtpHost": "mydomain.smtp.com",
    "EmailRecipients": "[email protected];[email protected]"
}   

Matching model class

namespace MyApp.Models
{
    public class AppSettingsModel
    {
        public string SmtpHost { get; set; }
        public string EmailRecipients { get; set; }
    }
}

Then populate that model class and add it to the IOptions collection in the DI container (this is done in the Configure() method of the Startup class).

services.Configure<AppSettingsModel>(Configuration.GetSection("ApplicationSettings"));

// Other configuration stuff

services.AddOptions();

Then you can access that class from any method that the framework calls by adding it as a parameter in the constructor. The framework handles finding and providing the class to the constructor.

public class MyController: Controller
{
    private IOptions<AppSettingsModel> settings;

    public MyController(IOptions<AppSettingsModel> settings)
    {
        this.settings = settings;
    }
}

Then when a method in a class library needs the settings, I either pass the settings individually or pass the entire object.