Question

我在visual studio 2012中创建了解决方案，这个解决方案是在4个项目中进行的：

项目表示层（asp.net mvc）

业务实体层

public class Parent
{
  public int Id {get; set;}
  public decimal TotalPrice {get; set;}
  //the rest of properties
  public private ICollection<Child> Children {get; set;}
}

public class Child
{
  public int Id {get; set;}
  public decimal UnitePrice {get; set;}
  //the rest of properties
  public int ParentId {get; set;}
  public private Parent Parent {get; set;}
}

数据访问层（ado.net数据模型实体框架+存储库）

//class repository for child
public class ParentRepository :IDisposable, IParentRepository
{
//implemente GetAll
   public IEnumerable<Parent>GetAllParents()
   {
      return context.parents;
   }
   public Parent GetParentById(int ParentId)
   {
      return context.Parents.Find(parentId);
   }

   //implemente GetAll CRUD for Parent
   public void AddParent(Parent parent)
   {
      context.Parents.Add(parent);
   }

   public void UpdateParent(Parent parent)
   {
      context.Parents.Attach(parent);
       context.Entry(Parents).State = EntityState.Modified;

   }

   public void DeleteParent(int parentId)
   {
      Parent parent = context.Parents.Find(parentId);
      context.Parents.Remove(parent);
   }
   // save methode
   public int Save()
   {
      return context.SaveChanges();
   }
} 

//class repository for child
public class ChildRepository : IDisposable,IChildRepository
{

EFContext context = new EFContext();

//Get the children for one parent

public IEnumerable<Child> GetAllChildrenByParentId(int parentId)
{
   var query = context.Children.Where(c=>c.ParentId == parentId)
}

  //the rest of code to implemente CRUD of children

  public Child GetChildById(int childId)
  {
     return context.Children.Find(childId);
  }

  //implemente CRUD for Child
  public void AddChild(Child child)
  {
     context.Children.Add(child);
  }

  public void UpdateChild(Child child)
  {
    context.Children.Attach(child);
    context.Entry(child).State = EntityState.Modified;

  }

  public void DeleteChild(int childId)
  {
     Child child = context.Children.Find(childId);
     context.Children.Remove(child);
  }
  // save methode
  public int Save()
  {
     return context.SaveChanges();
  }
}

但是对于Bll类中的业务逻辑层，我尝试通过子项的单位价格总和来计算父项的总数

public class ParentChildBll
{
  //retreive the parent by its parentid
   public Parent GetParent(int parentId){
      using (var repository = new ParentRepository())
      {       
        return repository.GetParentById(parentId);
      }  
   }
   public decimal GetTotal(int parentId)
   {
      int total;
      //call the GetParent() methode for getting parent to update its totalprice
      Parent parent = GetParent(parentId);
      //call the methode GetAllChildrenByParentId of ChildRepository that return 
     //ienumerebal<Child> and then call the extention methode Sum for calculate 
    // the sum of unite prices of child

     using (var repository = new ChildRepository())
     {       
        var query = reopsitory.GetAllChildrenByParentId(parentId).Sum(d=>d.UnitePrice);
       total=query;
     }

     parent.TotalPrice =total;
     UpdateParent(parent);//call update parent
     return total;
 }
 //implement crud parent
 public void UpdateParent(Parent parent)
 {
   //call repository update methode in BLL class
   using (var repository = new ParentRepository())
   {       
       reopsitory.UpdateParent(parent);
       repository.Save();
   }
   //
  }
}

我尝试过：

- 每次插入/更新/删除子项时我都必须调用getTotal（）方法来更新ParentChildBLL类中的父级totalprice，

public void AddChild(Child child)
{
   //call repository update methode in BLL class
   using (var repository = new ChildRepository())
   {       
       reopsitory.AddChild(child);
       repository.Save();
   }
   //update totalPrice of parent each insertion of child
   getTotal(child.ParentId);
}

当插入/更新/删除子项时，每个子unitprice的总和是否有更好的实现更新父总数

-i不知道必须在存储库或Bll中实现calculte总和在哪里？

如果你帮助我，我将不胜感激。

很快就好了

Answer 1

一般情况下，我们避免存储计算出的属性，但如果符合以下条件则可能有用：

涉及子实体，
子实体的更新频率低于检索父实体的次数。

当插入/更新/删除子项时，每个子unitprice的总和是否有更好的实现更新父总数

考虑更新差异：

public class ParentChildBll
{
    public decimal UpdateTotal(int parentId, decimal oldUnitPrice, decimal newUnitPrice)
    {
        var parent = GetParent(parentId);
        parent.TotalPrice += newUnitPrice - oldUnitPrice;
        UpdateParent(parent);
    }

    public void AddChild(Child child)
    {
        var oldUnitPrice = 0m;
        var newUnitPrice = child.UnitePrice;

        using (var repository = new ChildRepository())
        {
            repository.AddChild(child);
            repository.Save();
        }

        UpdateTotal(child.ParentId, oldUnitPrice, newUnitPrice);
    }
}

Answer 2

首先在EF代码中，您可以使用computed column来存储TotalPrice。它应该是read-only字段。

public class Parent
{
    public int Id { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public decimal TotalPrice
    {
        get
        {
            return Children == null ? 0 : Children.Sum(x => x.UnitePrice);
        }
    }

    //the rest of properties
    public virtual ICollection<Child> Children { get; set; }
}

Answer 3

您只需在linq代码中使用sum函数即可从数据库获取父母

例如在业务层中为您编写代码

 public IEnumerable<Parent>GetAllParents()
 {
      return context.parents.Select(p=> new Parent 
      {
       Id = p.Id,
       TotalPrice = p.Children.Sum(x=>x.UnitePrice)
      });
}

我认为不需要UpdateTotal方法

从子总和记录更新父级

3 个答案: