在实体框架，如何保存之前调用方法对实体 [英] in Entity framework, how to call a method on Entity before saving

问题描述

下面我创建了一个演示实体来证明什么IAM寻找

Below i have created a demo entity to demonstrate what iam looking for

public class User :  IValidatableObject
{
      public string Name{get;set;}

      [Required]
      public DateTime CreationDate{get;set;}

      public DateTime UpdatedOnDate{get;set;}

      public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
      {
          if(Name="abc")
          {
           yield return new ValidationResult("please choose any other name then abc", new[] { "Name" });
          }
      }
}

我在执行 IValidatableObject 界面，使这个实体SelfValidating。

I am implementing IValidatableObject interface to make this entity SelfValidating.

现在目前来创建新的用户IAM这样

Now currently to create new User iam doing this

 User u= new User();
 u.Name="Some name";
 u.CreationDate=DateTime.Now
 dbContext.Users.Add(u);
 dbContext.SaveChanges();

荫规划转向 u.CreationDate = DateTime.Now; User类的内部代码。和实施提供了将在保存之前并验证IAM寻找$

Iam planning to shift u.CreationDate=DateTime.Now; code inside User class. And implement an interface that provides a method which will be executed before saving and after validating

// class structure that iam looking for

 public class User :  IValidatableObject,IMyCustomInterFace
 {
     //rest codes as above class

     public void MyMethod(Whatever)
     {
        //this method gets called after Validate() and before save

        if(dataContext.Entry<User>(this).State == System.Data.EntityState.Added)
        {
            //add creation date_time
            this.CreationDate=DateTime.Now;

            //SET MORE DEFAULTS
        }

        if(dataContext.Entry<User>(this).State == System.Data.EntityState.Modified)
        {
            //update Updation time
            this.UpdatedOnDate=DateTime.Now;
        }
     }
 }

现在来创建一个新用户我只需要如下做，
注意我没有加入日期属性此时，类并自动

now to create a new user i just have to do as below, note i didnt added date property this time, Class does that automatically

User u= new User();
u.Name="Some name";
dbContext.Users.Add(u);
dbContext.SaveChanges();

要更新的用户， UpdatedOnDate 属性将为按类别自动更新

To update user, UpdatedOnDate property will be automatically updated by class

User u= getUserFromSomeWhere();
u.Name="Updated Name";
dataContext.Entry<User>(u).State = System.Data.EntityState.Modified;
dbContext.SaveChanges();

我的提问：是否有任何现有的接口，提供
有些方法被保存前，验证或其他一些方法后称为$这样做的b $ b，我可能不会知道。

My Question: is there any existing interface that provides some method that gets called before Save and After Validate or some other ways of doing this, that i may not be knowing.

或者，如果我创建自定义接口如何使获得在我寻找

Or if I create my custom interface how can i make its method to get executed in the order i am looking for

推荐答案

我有一个几乎相同的情况下，我的顺序执行的方法通过处理 SavingChanges 上下文事件管理。

I have an almost identical situation and I manage it by handling the SavingChanges event on the context.

首先，我创建定义时间戳操作的接口：

First I create an interface that defines the timestamping operations:

public interface IHasTimeStamp
{
    void DoTimeStamp();
}

然后我在实体实现这个接口：

Then I implement this interface in my entities:

Public class User : IHasTimeStamp
(
    public void DoTimeStamp()
    {
        if(dataContext.Entry<User>(this).State == System.Data.EntityState.Added)        
        {            
            //add creation date_time            
            this.CreationDate=DateTime.Now;            
        }        

        if(dataContext.Entry<User>(this).State == System.Data.EntityState.Modified)        
        {            
            //update Updation time            
            this.UpdatedOnDate=DateTime.Now;        
        }
    }
}

最后一步是注册SavingChanges处理程序，并实现它。

The final step is to register the SavingChanges handler and implement it.

public partial class MyEntities
{
    partial void OnContextCreated()
    {
        // Register the handler for the SavingChanges event.
        this.SavingChanges
            += new EventHandler(context_SavingChanges);
    }

    // SavingChanges event handler.
    private static void context_SavingChanges(object sender, EventArgs e)
    {
        // Validate the state of each entity in the context
        // before SaveChanges can succeed.
        foreach (ObjectStateEntry entry in
            ((ObjectContext)sender).ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified))
        {
            if (!entry.IsRelationship && (entry.Entity is IHasTimeStamp))
            {
            (entry.Entity as IHasTimeStamp).DoTimeStamp();
            }
        }
    }
}

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