您所追求的是对象的factory method pattern 和数据访问代码的repository pattern。我无法像文章那样解释它，所以我将介绍基本思想并提供一些示例。
目标是将您的代码库划分为处理一种特定类型的关注点的层，例如与用户 (UI) 通信、在应用程序中保存和验证数据（业务类/模型）或管理数据持久性（数据访问）。保持这些区域整齐划分可以更容易地维护和调试代码或并行开发。还有其他好处，例如促进跨多台物理机器的架构，但这超出了问题的范围。
基本结构：
获取概念进展：
UI -> Person Factory -> Person class -> Repository -> Database
保存概念进展：
UI -> Person class -> Repository -> Database
Person 类结构，内部带有解释性 cmets：
public class Person
{
// various properties & methods
// Constructor access is restricted to control how the class gets consumed.
// All instance management must go through the factories.
protected Person() { /* stuff */ }
// Person factory implementation. It's done inside the Person class so that
// tight control can be kept over constructor access.
// The factory is what gives you your instances of Person.
// It has defined inputs and outputs, as well as more descriptive
// names than constructor overloads, so consumers know what to expect.
// It's also a place to put scaffolding code, so you can avoid doing
// things like setting properties every time you fetch an instance.
// The factory takes care of all the object initialization and returns
// an instance that's ready for use.
public static Person GetPerson(int id)
{
Person p = new Person();
// here you call the repository. It should return either a native
// data structure like DataReader or DataTable, or a simple DTO class
// which is then used to populate the properties of Person.
// the reason for this is to avoid a circular dependency between
// the repository and Person classes, which will be a compile time error
// if they're defined in separate libraries
using(PersonRepository repo = new PersonRepository())
{
DataReader dr = repo.GetPerson(id);
p.FillFromDataReader(dr);
}
return p;
}
protected void FillFromDataReader(DataReader dr)
{ /* populate properties in here */ }
// Save should be an instance method, because you need an instance of person
// in order to save. You don't call the dealership to drive your car,
// only when you're getting a new one, so the factory doesn't do the saving.
public void Save()
{
// Again, we call the repository here. You can pass a DTO class, or
// simply pass the necessary properties as parameters
using(PersonRepository repo = new PersonRepository())
{
this.Id = repo.SavePerson(name, address);
}
}
}
现在，存储库代码：
// This class implements IDisposable for easy control over DB connection resources.
// You could also design and implement an IRepository interface depending on your needs.
public class PersonRepository : IDisposable
{
private SqlConnection conn;
public PersonRepository()
{
// in here you initialize connection resources
conn = new SqlConnection("someConnectionString");
}
public void IDisposable.Dispose()
{
// clean up the connection
conn.Dispose();
}
// The instance methods talk to the database
public int SavePerson(string name, string address)
{
// call your stored procedure (or whatever) and return the new ID
using(SqlCommand cmd = conn.CreateCommand())
{
// stuff
return (int)cmd.Parameters["myOutputIDParameter"].Value;
}
}
public DataReader GetPerson(int id)
{
// call your stored procedure (or whatever) and return the fetched data
using(SqlCommand cmd = conn.CreateCommand())
{
// stuff
return cmd.ExecuteReader();
}
}
}
最后，您将在 UI 级别执行以下操作：
Person joe = Person.GetPerson(joeId);
// stuff
joe.Save();