使用EF 4.1将父记录和多个子记录插入单个“工作单位” [英] Using EF 4.1 Inserting a parent record and multiple child records as a single "Unit of Work"

问题描述

我正在练习一个具有父子关系的第一组代码。

  public class Parent 
 {
 public int Id（get; set;} 
 public string name {get; set;} 
 public List< Child> Children {get; set;} 
 
 public Parent（）
 {
 Children = new List& Child>（）; 
} 
} 
 
 public class Child（）
 {
 public int Id（get; set;} 
 public string Name {get; set;} 
} 
 
 public class MyContext：DbContext 
 {
 public DbSet< Parent> Parents {get; set;} 
 public DbSet< Child>儿童{get; set;} 
} 
  

简单的控制台应用程序我创建一个父项并创建两个子记录，并将它们添加到父项，如果然后调用SaveChanges（），则只有第一个孩子被添加到children表中。

  var x = new MyContext（）; 
 
 var c1 = new Child {Name =Alpha-Child}; 
 var c2 = new Child {Name =Beta-Child}; 
 
 var p = new家长{Name =Alpha-Parent}; 
 
 p.Children.Add（c1）; 
 p.Children.Add（c2）; 
 
 x.Parents.Add（p）; 
 
 x.SaveChanges（）; 
  

那不是我想要的，所以我试图添加到父对象和上下文对象。

  var x = new MyContext（）; 
 
 var c1 = new Child {Name =Alpha-Child}; 
 var c2 = new Child {Name =Beta-Child}; 
 
 var p = new Parent {Name =Alpha-Parent}; 
 
 p.Children.Add（c1）; 
 p.Children.Add（c2）; 
 
 x.Children.Add（c1）; 
 x.Children.Add（c2）; 
 
 x.Parents.Add（p）; 
 
 x.SaveChanges（）; 
  

将子记录都存入数据库，但只有一个（第一个）被关联与父记录。

最后但并非最不重要的是，我每次调用Parent.Add（）之后，都调用SaveChanges（）。

  var x = new MyContext（）; 
 
 var c1 = new Child {Name =Alpha-Child}; 
 var c2 = new Child {Name =Beta-Child}; 
 
 var p = new Parent {Name =Alpha-Parent}; 
 
 x.Parents.Add（p）; 
 
 p.Children.Add（c1）; 
 x.SaveChanges（）; 
 
 p.Children.Add（c2）; 
 x.SaveChanges（）; 
  

但是，这打破了我对工作单位模式如何工作的想法。我应该能够调用SaveChanges（）一次，并且所有的更改都会发生，正确吗？

那么我做错了什么？

解决方案

以下代码将保存在单个保存更改中，并始终使用transactionscope单独保存。

  public class Child 
 {
 public int Id（get; set;} 
 public string Name {get; set; } 
 public Parent Parent {set; get;} 
} 
 
 
 var x = new MyContext（）; 
 var c1 = new Child {Name =Alpha-Child}; 
 var c2 = new Child {Name =Beta-Child}; 
 
 var p = new Parent {Name =Alpha-Parent}; 
 c1.Parent = p; 
 c2.Parent = p; 
 x.Parents.Add（p）; 
 x.SaveChanges（）; 
  

I am practicing with a code-first set of classes with a parent-child relationship between them.

public class Parent
{
    public int Id ( get; set; }
    public string Name { get; set; }
    public List<Child> Children { get; set; }

    public Parent()
    {
        Children = new List<Child>();
    }
}

public class Child()
{
    public int Id ( get; set; }
    public string Name { get; set; }
}

public class MyContext : DbContext
{
    public DbSet<Parent> Parents { get; set; }
    public DbSet<Child> Children { get; set; }
}

In a simple console app I create a parent and create two child records and add them to the parent. If I then call the SaveChanges() only the first child is added to the children table.

var x = new MyContext();

var c1 = new Child { Name = "Alpha-Child" };
var c2 = new Child { Name = "Beta-Child" };

var p = new Parent {Name = "Alpha-Parent"};

p.Children.Add(c1);
p.Children.Add(c2);

x.Parents.Add(p);

x.SaveChanges();

Well that was not what I wanted, so I tried to maybe add then to both the parent object and the context object.

var x = new MyContext();

var c1 = new Child { Name = "Alpha-Child" };
var c2 = new Child { Name = "Beta-Child" };

var p = new Parent {Name = "Alpha-Parent"};

p.Children.Add(c1);
p.Children.Add(c2);

x.Children.Add(c1);
x.Children.Add(c2);

x.Parents.Add(p);

x.SaveChanges();

That got both the child records into the database, but only one of them (the first) was associated with the parent record.

Last, but not least, I tried to do a call to SaveChanges() after each call to Parent.Add().

var x = new MyContext();

var c1 = new Child { Name = "Alpha-Child" };
var c2 = new Child { Name = "Beta-Child" };

var p = new Parent {Name = "Alpha-Parent"};

x.Parents.Add(p);

p.Children.Add(c1);
x.SaveChanges();

p.Children.Add(c2);
x.SaveChanges();

But, this breaks my idea of how the "Unit of Work" Pattern works. I "Should be able to call SaveChanges() once, and have all my changes take place, correct?

So, what am I doing wrong?

解决方案

The following piece of code will save in single save changes. And always use a transactionscope to save in single batch.

public class Child 
{
  public int Id ( get; set; }
  public string Name { get; set; }
  public Parent Parent {set;get;}
}


var x = new MyContext();
var c1 = new Child { Name = "Alpha-Child" };
var c2 = new Child { Name = "Beta-Child" };

var p = new Parent {Name = "Alpha-Parent"};
c1.Parent = p;
c2.Parent = p;
x.Parents.Add(p);
x.SaveChanges();

这篇关于使用EF 4.1将父记录和多个子记录插入单个“工作单位”的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！