Question

我正在尝试构建一个与我的asp.net Web应用程序中的数据库交互的类。我需要你对如何设计它的意见，这是我想到的一个例子

public class Person
{
    int personId;
    string name;
    string lastName;

    public int PersonId
    {
        get { return personId; }
    }

    public string Name
    {
        get { return name; }
        set { name = value; }
    }

    public string LastName
    {
        get { return lastName; }
        set { lastName = value; }
    }

    public Person()
    {

    }

    public static void Save(Person p)
    {
        //datalayer here
        //save the person class
    }

    public static Person GetPerson(int person_id)
    {
        //datalayer here
        //get the person from database and return a person class
        Person p = new Person();
        p.personId = 10;
        p.name = "Alex";
        return p;
    }
}

这样我就可以使用数据库方法而无需实例化类：

Person p = Person.GetPerson(19);
p.Name = "Alex...";
Person.Save(p);

感谢您的帮助。

Answer 1

使用Automatic条款，因为您的私人字段在代码中的功能相同。

我认为，Save是操作，可以在Person 实体的对象上完成。所以我不会把它作为静态方法。我会将您的Save代码移动为Person对象的方法。所以我会称之为obj.Save()。要加载数据，我会使用我的类constructor的重载版本。

public class Person
{
    int personId;      

    public int PersonId
    {
        get { return personId; }
    }    
    public string Name { set;get;}   
    public string LastName { set;get;}        

    public Person() {}

    public Person(int person_id)
    {
        //call to datalayer here
        //get the person from database and return a person class          
        personId = 10;
        Name= "Alex";  // set the public property value here           
    }
    public bool Save()
    {
        //datalayer here
        //save the person class and return
      // true/false /or new ID (change return type)
    }    

}

在致电时，

Person p = new Person(19);  //get existing person
p.Name = "New Name";
p.Save();

编辑：另一种（更好的）方法是将您的实体类保持为简单的POCO。这意味着那里没有数据访问/ BL代码。它看起来就像

public class Person
{
  public int ID { set;get;}
  public string Name { set;get;}
}

并有Repository为您执行数据操作。所以你的存储库可能有像这样的方法

public interface IRepository
{ 
   Person GetPerson(int id);
   bool SavePerson(Person person);
}

您可以在类中实现此Interface来执行数据访问操作

public class Repository:IRepository
{
  //implementation of your DA methods here
}

现在您可以从不同的层（业务层）中调用它，就像这样

IRepository repo = new Repository();

var person=repo.GetPerson(19);  
person.Name="Updated Name";
repo.Save(person);

Answer 2

我喜欢持久性无知的事情：What are the benefits of Persistence Ignorance?）

在这种情况下，您应该将Save方法移动到另一个类，以便实体不包含任何应该如何保留它的信息。

Answer 3

您所追求的是对象的factory method pattern和数据访问代码的repository pattern。我无法解释它几乎与文章一样，所以相反，我将讨论基本的想法并提供一些例子。

目标是将代码库划分为处理一种特定关注类型的层，例如与用户（UI）通信，保存和验证应用程序中的数据（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。还有其他一些好处，例如促进跨多个物理机器的架构，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，里面有解释性注释：

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，这是你在UI级别所做的事情：

Person joe = Person.GetPerson(joeId);
// stuff
joe.Save();

Answer 4

你做对了，但你也可以为你上课使用自动属性。它可以节省你的一些时间。例如

public class Person
{

    public int PersonId { get; set;}    
    public string Name { get; set;}
    public string LastName { get; set;}

    public Person()
    {
    }
}

班级＆amp;在C＃中的方法，这是一个很好的方法吗？

4 个答案: