c# - C#中的类设计结构

Question

实体类:

public class Customer {
        public int CustomerId { get; set; }
        public string Name { get; set; }
}

public class Invoice {
        public int InvoiceId { get; set; }
        public int CustomerId { get; set; }
        public string InvoiceNo { get; set; }
}

接口(interface):

public interface ICustomerService {
    Customer GetCustomerById(int customerId);
    void DeleteCustomer(int customerId);
}

public interface IInvoiceService {
    Invoice GetInvoiceById(int invoiceId);
    void DeleteInvoice(int invoiceId);
    List<Invoice> GetAllInvoiceByCustomer(int customerId);
    Customer GetInvoiceCustomer(int invoiceId);
}

类:

public class CustomerService : ICustomerService {

    private readonly IInvoiceService _invoiceService = new InvoiceService();

    public Customer GetCustomerById(int customerId) {
        //return customer from db
        return new Customer();
    }

    public void DeleteCustomer(int customerId) {
        var invoiceList = _invoiceService.GetAllInvoiceByCustomer(customerId);
        foreach (var invoice in invoiceList) {
            _invoiceService.DeleteInvoice(invoice.InvoiceId);
        }

        //delete customer from db

    }
}

public class InvoiceService : IInvoiceService {

    private readonly ICustomerService _customerService = new CustomerService();

    public Invoice GetInvoiceById(int invoiceId) {
        //return invoice from db
        return new Invoice();
    }

    public void DeleteInvoice(int invoiceId) {
        //delete invoice from db
    }

    public List<Invoice> GetAllInvoiceByCustomer(int customerId) {
        //get all invoice by customer id
        return new List<Invoice>();
    }

    public Customer GetInvoiceCustomer(int invoiceId) {
        Invoice invoice = GetInvoiceById(invoiceId);
        return _customerService.GetCustomerById(invoice.CustomerId);
    }

}

当我为“CustomerService”创建一个新实例时。它将返回一个错误:

An unhandled exception of type 'System.StackOverflowException' occurred

因为当我为“CustomerService”创建新实例时，“CustomerService”会为“InvoiceService”创建一个新实例，“InvoiceServer”也会创建一个“CustomerServer”的新实例。

1) 我应该将所有方法都设置为静态吗？

2) “InvoiceService”将调用“CustomerService”的方法，“CustomerService”也会调用“InvoiceSercie”的方法。我该如何编写类(class)？如果我将所有方法设置为静态，问题将得到解决，但我想这不是一个好的解决方案。

非常感谢!

Answer 1

您必须选择其中一个类将其自身作为对另一个类的引用。假设它是客户服务:

public class CustomerService : ICustomerService {

  private readonly IInvoiceService _invoiceService = new InvoiceService(this);

  ...
}

public class InvoiceService : IInvoiceService {

  private readonly ICustomerService _customerService;

  public class InvoiceService(ICustomerService customerService) {
    _customerService = customerService;
  }

}

现在这个循环被打破了...

另一种选择是使用依赖注入(inject)框架，如 StructureMap 或 Ninject。