How to get IOptions in ConfigureServices method or pass IOptions into extension method?

For binding data from appsettings.json to Model, you could follow steps below:

1. Appsettings.json content

   {
   "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
       "Default": "Warning"
          }
    },      
    "JWT": {
         "Issuer": "I",
         "Key": "K"
       }
    }
   

2. JWT Options

   public class JwtOptions
   {
       public string Issuer { get; set; }
       public string Key { get; set; }
    }
   

3. Startup.cs

   public void ConfigureServices(IServiceCollection services)
   {
       services.Configure<JwtOptions>(Configuration.GetSection("JWT"));
       var serviceProvider = services.BuildServiceProvider();
       var opt = serviceProvider.GetRequiredService<IOptions<JwtOptions>>().Value;
       services.AddJwtAuthentication(opt.Issuer, opt.Key);
       services.AddMvc();
   }
   

4. One more option to pass JwtOptions directly.

   public void ConfigureServices(IServiceCollection services)
   {
       services.Configure<JwtOptions>(Configuration.GetSection("JWT"));
       var serviceProvider = services.BuildServiceProvider();
       var opt = serviceProvider.GetRequiredService<IOptions<JwtOptions>>().Value;
       services.AddJwtAuthentication(opt);
   
       services.AddMvc();
   }
   

5. Change the extension method.

   public static IServiceCollection AddJwtAuthentication(this IServiceCollection services, JwtOptions opt)
   

One other option is to bind the configurations to a class with the Bind() extension. (IMO this a more clean solution then the IOptions)

public class JwtKeys
{
    public string Issuer { get; set; }
    public string Key { get; set; }
}

public void ConfigureServices(IServiceCollection services)
{
    var jwtKeys = new JwtKeys();
    Configuration.GetSection("JWT").Bind(JwtKeys);

    services.AddJwtAuthentication(jwtKeys);
}

public static IServiceCollection AddJwtAuthentication(this IServiceCollection services, JwtKeys jwtKeys)
{....}

Then if you need the JwtKeys settings some other place in the solution, just register the class on the collection and inject it where needed

services.AddSingleton(jwtKeys);