I'm now trying DI in ASP.NET Core.
I created a singleton object, and saved some application information to it.
I could inject Dependency into constructors, razor pages and repositories but don't know how to inject into entity.

MyConfig.cs:

  public interface IMyConfig
  { ... }
  
  public class MyConfig:IMyConfig
  {
    public MyConfig() {}

    public string CompanyName { get { return _companyName; } }
    public string ContactEMail { get { return _contactEmail; } }
  }

program.cs:

builder.Services.AddSingleton<IMyConfig, MyConfig>();  // application information
builder.Services.AddSingleton<IMyRep, MyRep>();        // my repository

Repositories.cs:

  public interface IMyRep
  {
    public string GetCompanyName();
    public IEnumerable<IUser> GetUsers();
  }

  public class MyRep : IMyRep
  {
    private readonly DbContext _context;
    private readonly MyConfig _config;

    public MyRep(DbContext context, MyConfig config)
    {
      _context = context;
      _config = config;
    }

    public string GetCompanyName() { return _config.CompanyName; }
    public string GetContactEmail() { reutnr _config.ContactEmail; }

    public GetUsers()
    {
      _context.Users.Select(m => m);
    }
  }

All above codes worked.

In addtion to above, I want to inject MyConfig to User entity.
It contains specific MyConfig information in User, like following.

user.cs:

public interface IUser
{
  public int Id { get;set; }
  public string Name { get;set; }
  public string Company { get; }
}
public class User: IUser
{
  private readonly IMyConfig _config;
  public User(IMyConfig config)
  {
    _config = config;
  }
  public int Id { get;set; }
  public string Name { get;set; }
  public string Company { get { return _config.CompanyName; } }
}
 

Although I was tried to implement following code in program.cs, didn't work.

builder.Services.AddSingleton<IUser, User>();

Can I inject the object into the entity?

CodePudding user response：

I will provide a simple example based on your code and point out the problem in your code:

MyConfig.cs:

public interface IMyConfig
    { 
        string CompanyName { get; }
        string ContactEMail { get; }
    }

    public class MyConfig : IMyConfig
    {
        public MyConfig() { }

        public string CompanyName { get { return "Company"; } }
        public string ContactEMail { get { return "Email"; } }
    }

Repositories.cs:

When injecting MyConfig, the interface IMyConfig should be injected, not the implementation method.

public interface IMyRep
    {
        public string GetCompanyName();
        public string GetContactEmail();
        public IEnumerable<IUser> GetUsers();
    }

    public class MyRep : IMyRep
    {
        private readonly MyDbContext _context;
        private readonly IMyConfig _config;

        public MyRep(MyDbContext context, IMyConfig config)
        {
            _context = context;
            _config = config;
        }

        public string GetCompanyName() { return _config.CompanyName; }
        public string GetContactEmail() { return _config.ContactEMail; }

        public IEnumerable<IUser> GetUsers()
        {
            return _context.Users.Select(m => m);
        }
    }

user.cs:

public interface IUser
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Company { get; }
    }
    public class User : IUser
    {
        private readonly IMyConfig _config;
        public User(IMyConfig config)
        {
            _config = config;
        }
        public int Id { get; set; }
        public string Name { get; set; }
        public string Company { get { return _config.CompanyName; } }
    }

program.cs:

IMyConfig,IMyRep, IUser should be registered as Scoped.

builder.Services.AddScoped<IMyConfig, MyConfig>(); 
builder.Services.AddScoped<IMyRep, MyRep>();
builder.Services.AddScoped<IUser, User>();

Then I can successfully pass MyConfig.CompanyName to User.Company:

public class HomeController : Controller
{
    private readonly IUser _user;
    public HomeController(IUser user)
    {
        _user = user;
    }
    public IActionResult Index()
    {
        var Company = _user.Company;
        return View();
    }
}

Is this what you expected?