I'm new with C# and my console application for some reason the interface IService doesn't transfer the value to the Service. I tried to debug: _service.GetAccountName(name), name has value and then I get System.NullReferenceException for _service.GetAccountName. What I'm doing wrong here? Thank you for your patience.

Program:

static void Main(string[] args)
{
    var newMenu = new Menu();
    newMenu.Show();

}

Menu

 public class Menu
{
    private IService _service { get; set; }

    public void Show()
    {

        var shouldStop = "";

        while (shouldStop.ToLower() != "yes")
        {
            Console.WriteLine("Please select one of the following options:");
            Console.WriteLine("1.Create BC \n2.View BC\n3.Edit BC\n4.Delete BC");
            var response = int.Parse(Console.ReadLine());

            switch (response)
            {
                case 1:
                    Console.WriteLine("You choose to create bank account");
                    ChooseTypeOfAccount();
                    break;
                case 2:
                    Console.WriteLine("You choose to view bank account");
                    var user = ChooseToViewBankAccount();
                    if (user != null)
                    {
                        Console.WriteLine("Id:"   user.Id   "\n"  user.Name   "\n"   user.Surname);
                    }
                    else
                    {
                        Console.WriteLine("User can not be found");
                    }

                    Console.WriteLine("ALL USERS");
                    var allUs = _service.GetAllUsers();
                    for(var i = 0; i < allUs.Item1.Count; i  )
                    {
                        Console.WriteLine(allUs.Item1[i].Name   " "   allUs.Item1[i].Surname);
                        for(var j = 0; j < allUs.Item2.Count; j  )
                        {
                            Console.WriteLine(allUs.Item2[i].Name   " "   allUs.Item2[i].Surname);
                        }
                    }

                    break;
                case 3:
                    Console.WriteLine("You choose to edit BC");
                    break;
                case 4:
                    Console.WriteLine("You choose to delete BC");
                    break;
                default:
                    Console.WriteLine("oops wrong choice");
                    break;
            }
            Console.WriteLine("To exit type yes");
            shouldStop = Console.ReadLine();
        }

        

    }

    private User ChooseToViewBankAccount()
    {
        Console.WriteLine("Please enter your name");
        var name = Console.ReadLine();

        User user = _service.GetAccountByName(name);

        return user;
    }

Service:

public class Service : IService
{
    public AccountsData _accountsRepository { get; set; }

    public ChildAccountsData _childAccountRepository { get; set; }


    public Service()
    {
        _accountsRepository = new AccountsData();
        _childAccountRepository = new ChildAccountsData();
    }

IService

public interface IService
{
    User GetAccountByName(string name);
    void CreateRegularAccount(string name, string surname);
    void CreateChildAccount(string childName, string childSurname);
    (List<Account>, List<ChildAccount>) GetAllUsers();
}

CodePudding user response：

as currently written you need to do

static void Main(string[] args)
{
    var newMenu = new Menu();
    newMenu.Service = new Service();
    newMenu.Show();

}

you would need ot change

      private IService _service { get; set; }

to

      public IService _service { get; set; }

but thats probably not what you want (allow callers to change Service as you go along). SO do this

       private IService _service = new Service();

PS, dont call you service IService call it something useful like IDBAccess or somethig like that.

CodePudding user response：

the most common way is to use dependency injection using a constructor.

 var newMenu = new Menu(new Service ());

but you will need to add the constructor to Menu class

 public class Menu
{
    private IService _service { get; set; }

   public Menu (IService service)
{
         _service = service;
}

....
}

or less popular way

var newMenu= new Menu { Service = new Service()}

but in this case you will have to change Service property to public

public class Menu
{
    public IService Service { get; set; }
   .....
}