如何在启动 class 中使用强类型配置

Question

I have a strongly-typed config working but I am struggling with using the strongly-typed class within the "class Startup"

Here is my code in startup:

public class Startup
{
    public IConfiguration Configuration { get; }

    public Startup(IHostEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);

        builder.AddEnvironmentVariables();
        Configuration = builder.Build();
    }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        // Allow sites to hit the API
        services.AddCors();

        // Add Mvc Routes
        services.AddMvc(option => option.EnableEndpointRouting = false);

        // Add custom configuration
        services.Configure<Config>(Configuration);

I'd like to use the strongly-typed class in another function in that file, but I'm not sure how I can do that...

This is how it works in other classes:

    readonly Config Config = null;

    public EmailController(IOptions<Config> config) 
    {
        Config = config.Value;
    }

But if I try to add the same code to my "class Startup" then I get this exception

System.ArgumentNullException: 'Value cannot be null. (Parameter 'config')'

on the line

services.Configure<Config>(Configuration);

Answer 1

I think you are asking how can you use your config inside the startup class before you are allowed to inject it into a constructor?

You can use Get or Bind methods on IConfiguration

// Add custom configuration
services.Configure<Config>(Configuration);

//Get the config object for use here
var config = Configuration.Get<Config>();