如何使用.Net 5 Core在其他类中全局访问appsettings.json

Question

I need access to the appsettings.json configuration in other non-controller classes in my project. Is there a good way for IConfiguration to be available globally throughout my application w/o using DI? If the IConfiguration DI could be used on non-controller classes, I'd like to know how to do that.

This is my controller where HostService has access to the IConfiguration injection.

public static IHostBuilder CreateHostBuilder(string[] args)
{
    return Host.CreateDefaultBuilder(args)
        .UseWindowsService()
        .ConfigureServices((hostContext, services) =>
        {
            services.AddHostedService<HostService>();
        }).UseSerilog();
}

I need access to IConfiguration in this non-controller class. I'm not sure how to use the DI w/ non-controller type classes, so maybe using a static type configuration variable would be a better solution to make IConfiguration available globally.

public class myTestClass 
{
    private readonly IConfiguration _config

    public myTestClass(IConfiguration config){ _config = config}
}

Answer 1

You can add a configuration to you DI container by adding a handling of config to you host:

public static IHostBuilder CreateHostBuilder(string[] args)
{
    return Host.CreateDefaultBuilder(args)
        .ConfigureAppConfiguration((hostContext, config) =>
        {
            config.AddJsonFile("appsettings.json", false, false);
        })
        .ConfigureServices((hostContext, services) =>
        {
            services.AddHostedService<HostService>();
        })
        .UseSerilog();
}

It makes the whole IConfiguration object available for your application:

public class TestOptions
{
    public string Data { get; set; }
}

public class HostService : BackgroundService
{
    private readonly IConfiguration _configuration;

    public HostService(IConfiguration config)
    {
        _configuration = config;
    }

    protected override Task ExecuteAsync(CancellationToken stoppingToken)
    {
        // TODO: write your code here
    }
}

I need access to IConfiguration in this custom class. I can pass an IConfiguration instance in from the HostService class, but was looking for global solution to avoid passing instances to other classes.

Dependency Injection solves a lot of different issues, and today it is a common way to develop software. It is much easier to use DI instead of avoid using it.

Answer 2

I actually figured out a way to make IConfiguration available throughout the application without using Injections. It's quite pointless to use IConfiguration DI for non-controller classes since it requires too many steps. Just create a static class w/ a static IConfiguration variable and assign the Iconfiguration injection parameter to it from the main controller class and it'll be available throughout the app. It's simple and easy.

Programs.cs

        public static IHostBuilder CreateHostBuilder(string[] args)
            {
                return Host.CreateDefaultBuilder(args)
                    .UseWindowsService()
                    .ConfigureServices((hostContext, services) =>
                    {
                        services.AddHostedService<HostService>();
                    }).UseSerilog();
            }   
        

HostService.cs

        public static class AppData
        {
            public static IConfiguration Config;
        }
        public class HostService : IHostedService, IDisposable
        {
            public HostSyncService(IConfiguration config)
            {
                AppData.Config = config;

                var key= new myTestClass().getKey();
            }
        }
        

myTestClass.cs

        public class myTestClass {
            public myTestClass(){}
            
            public void getKey(){
                // Non-Controller class has access to AppData.Config w/o injection
                var key= AppData.Config.GetValue<string>("appSettings:key");
            }
        }