如何在 Startup.cs 中实例化 singleton class 然后在网络核心中使用？

Question

I am creating an object from an object created in my appsetting.json, I add it through singleton but then I don't know how to access those values.

My class:

public class UserConfiguration
{
    public string Username { get; set; }
    public string Password { get; set; }
    public string SecretKey{ get; set; }
}

In my startup.cs

 var userCfg = Configuration.GetSection("UserConfig").Get<UserConfiguration>(); //.> success i've values
 services.AddSingleton(userCfg);

 services.AddControllers();

and i want use this class and I call this class from my controller api.

public class UserService : BaseService
{
    public UserService(IConfiguration config): base(configuration)
    {

    }

    public string GetData()
    {
        var userConfg = new UserConfiguration();
        var key = user.SecretKey;  //--> null but a instance is empty

        return "ok"
    }
}

but I don't know how to rescue the values of the singleton that I loaded in the Startup.cs

Answer 1

Since you're registering UserConfiguration as Singleton with DI container, you can inject this object UserService constructor:

public class UserService : BaseService
{
    private UserConfiguration _userConfiguration;
    public UserService(IConfiguration config, UserConfiguration userConfiguration): base(configuration)
    {
        _userConfiguration = userConfiguration; //Injected in constructor by DI container
    }

    public string GetData()
    {
        var key = _userConfiguration .SecretKey;

        return "ok"
    }
}

However recommended approach to pass application configuration information to services is by using the Options pattern

services.Configure<UserConfiguration>(Configuration.GetSection("UserConfig"));

services.AddControllers();

Add then access the configuration option:

public class UserService : BaseService
{
    private UserConfiguration _userConfiguration;
    public UserService(IConfiguration config, IOptions<UserConfiguration> userConfiguration): base(configuration)
    {
        _userConfiguration = userConfiguration.Value; //Injected in constructor by DI container
    }

    public string GetData()
    {
        var key = _userConfiguration .SecretKey;

        return "ok"
    }
}