您可以使用Dependency Injection，也就是说，它通常与让ContactController接受构造函数中的连接对象一样简单。通常，您会使用IConnection接口，而不是具体的连接类，以便模拟它进行测试。

namespace PruebaRestful.Services
{
    public class ContactRepository
    {
        private IConnection _connection;

        public ContactRepository(IConnection connection)
        {
            _connection = connection;
        }

        public Contact[] GetAllContacts()
        {
            return new Contact[]
            {
            new Contact
            {
                Id = 1,
                Name = "Glenn Block"
            },
            new Contact
            {
                Id = 2,
                Name = "Dan Roth"
            }
            };
        }
    }
}

要了解更多如何在Asp中执行此操作。净见https://learn.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection?view=aspnetcore-2.2

简而言之，你可以用任何方式（ADO.net或任何其他ORM）来做。
在您的场景中，您可以应用依赖项反转原则。
较高级别的模块不应依赖于较低级别的抽象
在您的情况下，消费者不应该知道数据是从哪里提供的。您所需要的只是更改GetAllContacts以使用ORM从数据库读取数据。

public class DbConnection: IConnection 
{
    // Code for managing DB Connection and data querying
}

public class ContactRepository: IContactRepository
{
    private IDbConnection _dbConnection;

    public ContactRepository(IConnection dbConnection)
    {
        _dbConnection= dbConnection;
    }

    public Contact[] GetAllContacts()
    {
         // Add code to read from DB here
    }
}

public class ContactController : ApiController
{
    private IContactRepository _contactRepository;

    public ContactController()
    {
        _contactRepository = <using any DI container resolve dependency with ContactRepository>;
    }

    public Contact[] Get()
    {
        return _contactRepository.GetAllContacts();        
    }
}