C#: Services access the dataprovider class running the sql statements - correct approach ?

Question

Hello,

is this a common and/or good approach?

In my ViewModel(Wpf) or Presenter(WinForms) I do this:

ICustomerService customerService = MyService.GetService<ICustomerService>();
ICustomerList customerList = customerService.GetCustomers();

the CustomerService class looks like this:

public class CustomerService : ICustomerService
{
     public ICustomerList GetCustomers()
     {
        return _customerDataProvider.GetCustomers();
     }
}

public class CustomerDataProvider()
{
    public ICustomerList GetCustomers()
    {
       // Open SQL connection,
       // get back a SqlDataReader and iterate it
       // in the loop write all data into a ICustomer object
       // add the ICustomer object to the ICustomerList
       // return ICustomerList object... 
    }
}

Answer 1

Retrieving data from a database is the plumbing of your application. And the less plumbing you have to write yourself, the more productive you will be.

I usually go to LINQ directly in the client:

 sp_GetCustomersResult customers;
 using (var db = new DbDataContext(ConnectionString))
      customers = db.sp_GetCustomers();

This works fairly well, and lets me focus on adding customer value instead of database access layers.

Answer 2

I haven't found much value in declaring interfaces for business classes or for custom collections since extension methods became available. I would have GetCustomers return IEnumerable<Customer>.

If you plan on working extensively with business objects then you should look into using an object/relation mapper such as NHibernate. Or use LINQ2SQL or Entity Framework to reduce the amount of repetitive plumbing code you have to write.