域驱动设计中的存储库

几个月来，我一直在与DDD作斗争，虽然我认为我对一些概念有一个相当好的想法，但我对实现应该如何工作，特别是应该如何从数据库加载数据不太有信心。我在C#只工作了六个月，这也于事无补。

[原始问题-见下文更新]

在我开始开发的应用程序中，我有一个包含基类的域命名空间，一个使用这些基类执行操作的服务命名空间，以及一个连接到数据库的存储库和DAL命名空间。

我认为最简单的方法是在服务命名空间中使用继承来添加LoadFromDb等过程，但当我开始实现时，我发现这个方法通常需要最多的代码，因为我必须两次分配所有类属性（一次在存储库命名空间中，然后在服务命名空间）。

下面是一个例子。我可以让选项2和选项3发挥作用，但我希望在精神上更接近选项1。

namespace Domain
{
    public class Request
    {
        public int RequestID{get; set;}
        public string RequestingUser {get; set;}
        public string Title {get; set;}
        public string Description{get; set;}
        public string status {get; set;}
    }
}

namespace app
{
    class MyApp
    {
        void Main()
        {
            //option 1
            Domain.Request x = new Service.svcRequest(5);
            //option 2
            Domain.Request y = new Service.svcRequest(5);
            //option 3
            Domain.Request z = new Domain.Request();
            Service.svcRequest2.loadRequest(5, z);
        }
    }
}
namespace Service
{
    public class svcRequest : Domain.Request
    {
        public svcRequest(int RequestID)
        {
            //this is what I want to do.  
            //  It fails because "this" is read-only 
            //  and because "this" can't be implicitly converted to DomainRequest.
            this = (Domain.Request)repos.Loads.LoadRequest(RequestID);
            //option 2, which is what I'm doing instead for now, but when you get 
            //  to 20 or 50 properties, it's a bit much, 
            //  esp. since those properties have already been assigned once 
            //  within the repository namespace.
            Domain.Request MyRequest = repos.Loads.LoadRequest(RequestID);
            this.RequestID = MyRequest.RequestID;
            this.RequestingUser = MyRequest.RequestingUser;
            this.Title = MyRequest.Title;
            this.Description = MyRequest.Description;
            this.status = MyRequest.status;
        }
    }
    public class svcRequest2
    {
        //option 3.  Much less code, but now I'm not really using inheritance, 
        //  so in my application layer I can't just declare my variable 
        //  and use the svcRequest constructor
        public static void loadRequest(int RequestID, Domain.Request MyRefRequest)
        {
            MyRefRequest = (Domain.Request)repos.Loads.LoadRequest(RequestID);
        }
    }
}
namespace repos
{
    public static class Loads
    {
        public static Domain.Request LoadRequest(int RequestID)
        {
            Domain.Request MyRequest = new Domain.Request();
            DataRow MyRow = dal.Loads.LoadRequestRow(RequestID);
            MyRequest.RequestID = RequestID;
            MyRequest.RequestingUser = (string)MyRow["User"];
            MyRequest.Title = (string)MyRow["Title"];
            MyRequest.Description = (string)MyRow["Description"];
            MyRequest.status = (string)MyRow["Status"];
            return MyRequest;
        }
    }
}
namespace dal
{
    public static class Loads
    {
        public static DataRow LoadRequestRow(int RequestID)
        {
            OleDbConnection dbCon = new OleDbConnection("Provider=SQLOLEDB;Data Source=dbServer;Initial Catalog=RequestDB;User ID=Joe;Password=password");
            string Select = "Select * from RequestTable where ID = " + RequestID;
            OleDbDataAdapter dbRequest = new OleDbDataAdapter(Select, dbCon);
            DataSet dsRequest = new DataSet();
            dbRequest.Fill(dsRequest);
            DataRow drRequest = dsRequest.Tables[0].Rows[0];
            return drRequest;
        }
    }
}

[更新]这是第二次尝试。我将Domain命名空间重命名为Model，并将Service命名空间重命名为Domain，我认为这更符合DDD约定。按照建议，我在DAL中使用的存储库名称空间中添加了一个接口。我现在唯一不能做的是选项1的Load语句，但我认为我只需要进一步研究继承。

我是不是越来越近了？

using System;
using System.Data;
using System.Data.OleDb;
namespace Model
{
    public class Request
    {
        public int RequestID{get; set;}
        public string RequestingUser {get; set;}
        public string Title {get; set;}
        public string Description{get; set;}
        public string status {get; set;}
    }
}

namespace App
{
    class MyApp
    {
        void Main()
        {
            //option 1
            Model.Request x = new Domain.dmnRequest(5);
            //option 2
            Model.Request y = new Domain.dmnRequest2(5);
            //option 3
            Model.Request z = new Model.Request();
            Domain.dmnRequest3.loadRequest(5, z);
        }
    }
}
namespace Domain
{
    public class dmnRequest : Model.Request, dal.Request
    {
        public dmnRequest(int requestID)
        {
            //this is what I want to do.  I'm not sure why it's failing
            Load(requestID); 
        }
    }
    public class dmnRequest2 : Model.Request
    {
        public dmnRequest2(int requestID) 
        {
            //option 2; it works but is cumbersome after you hit the 20th property
            dal.Request tmpRequest = new dal.Request();
            tmpRequest.Load(requestID);
            this.RequestID = tmpRequest.RequestID;
            this.RequestingUser = tmpRequest.RequestingUser;
            this.Title = tmpRequest.Title;
            this.Description = tmpRequest.Description;
            this.status = tmpRequest.status;
        }
    }
    public class dmnRequest3
    {
        //option 3.  Much less code, but now I'm not really using inheritance, so in my application layer I can't just declare my variable and use the dmnRequest constructor
        public static void loadRequest(int RequestID, Model.Request MyRequest)
        {
            dal.Request dalRequest = (dal.Request)MyRequest;
            dalRequest.Load(RequestID);
            MyRequest = (Model.Request)dalRequest;
        }
    }
}
namespace repos
{
    public interface SaveMe {void Save(int ID); }
    public interface LoadMe {void Load(int ID); }
}
namespace dal
{
    public class Request : Model.Request, repos.LoadMe
    {
        public void Load(int requestID)
        {
            OleDbConnection dbCon = new OleDbConnection("yaddayadda");
            string Select = "Select * from RequestTable where ID = " + requestID.ToString();
            OleDbDataAdapter dbRequest = new OleDbDataAdapter(Select, dbCon);
            DataSet dsRequest = new DataSet();
            dbRequest.Fill(dsRequest);
            DataRow drRequest = dsRequest.Tables[0].Rows[0];
            this.RequestID = requestID;
            this.RequestingUser = (string)drRequest["User"];
            this.Title = (string)drRequest["Title"];
            this.Description = (string)drRequest["Description"];
            this.status = (string)drRequest["Status"];
        }
    }
}