防止导航属性插入 [英] prevent navigation property insertion

问题描述

我有一个实体A，用作另一个实体B的导航属性。我想控制实体A的插入。这样，只要我插入AI，必须执行其他检查并更新其他实体。

但是当我插入类型B的实体时，它会自动插入连接的A实体，而不需要额外的检查和更新。

我该如何解决？ / p>

更新
我决定使用这个答案建议。但是在OnBeforeInsert（）中，我可能会在上下文中添加一个新的实体，因为在 var changedEntities = ChangeTracker.Entries（）;
我该如何解决？

解决方案

EF有很少的扩展点。所以有时很难自定义。

这个答案是我的以前的答案

  public抽象类Entity 
 {
 public virtual void OnBeforeInsert（）{} 
 public virtual void OnBeforeUpdate（）{} 
} 
 
 public class Category：Entity 
 {
 
 public string Name {get;组; } 
 public string UrlName {get;组; 
 
 public override void OnBeforeInsert（）
 {
 // ur logic 
} 
} 
  / pre> 
 
 
然后在您的 DbContext 类订阅 ObjectStateManagerChanged 事件 ObjectStateManager 。
  public class MyContext：DbContext 
 {
 public override int SaveChanges（）
 {
 //拦截实体更改
 UnderlyingObjectContext.ObjectStateManager.ObjectStateManagerChanged 
 + = OnObjectStateManagerChanged; 
 
 var changedEntities = ChangeTracker.Entries（）; 
 
 foreach（var changedEntity in changedEntities）
 {
 if（changedEntity.Entity是Entity）
 {
 var entity =（Entity）changedEntity.Entity ; 
 
 switch（changedEntity.State）
 {
 case EntityState.Added：
 entity.OnBeforeInsert（）; 
 break; 
 
 case EntityState.Modified：
 entity.OnBeforeUpdate（）; 
 break; 
} 
} 
} 
 
 return base.SaveChanges（）; 
} 
 
 ObjectContext UnderlyingObjectContext 
 {
 get 
 {
 return（（IObjectContextAdapter）this）.ObjectContext; 
} 
} 
 
 void OnObjectStateManagerChanged（object sender，CollectionChangeEventArgs e）
 {
 if（e.Action == CollectionChangeAction.Add）
 {
 //不是所有添加的实体都是新的
 if（UnderlyingObjectContext.ObjectStateManager 
 .GetObjectStateEntry（e.Element）.State == EntityState.Added）
 {
 if（e.Element is Entity）
 {
（（Entity）e.Element）.OnBeforeInsert（）; 
} 
} 
} 
} 
} 
  
如果您使用EF 4.0，则需要相应地进行自定义。
 
I have an entity A that used as navigation property for another entity B. I would like to control the Insertion for entity A. Thats meen that whenever I would insert A I have to perform other checks and update other entities.

But when I Insert entities of type B it automatically inserts the connected A entities without the extra checks and updates I need.

How can I solve this?

UPDATE
I decided to use this answer as suggested. But in the OnBeforeInsert() I might add a new entities to the context which their OnBeforeInsert() won't be called since in the time var changedEntities = ChangeTracker.Entries(); was called the new entitied wasn't exist yet.

How can I solve this?
解决方案
EF has very few extension points. So it is sometimes very difficult to customize.

This answer is an extension of my previous answer
public abstract class Entity
{
    public virtual void OnBeforeInsert(){}
    public virtual void OnBeforeUpdate(){}
}

public class Category : Entity
{

    public string Name { get; set; }
    public string UrlName{ get; set; }

    public override void OnBeforeInsert()
    {
       //ur logic
    }
}
Then in your DbContext class subscribe to ObjectStateManagerChanged event of ObjectStateManager.
public class MyContext : DbContext
{
    public override int SaveChanges()
    {
        //intercept entity changes
        UnderlyingObjectContext.ObjectStateManager.ObjectStateManagerChanged 
           += OnObjectStateManagerChanged;

        var changedEntities = ChangeTracker.Entries();

        foreach (var changedEntity in changedEntities)
        {
            if (changedEntity.Entity is Entity)
            {
                var entity = (Entity)changedEntity.Entity;

                switch (changedEntity.State)
                {
                    case EntityState.Added:
                        entity.OnBeforeInsert();
                        break;

                    case EntityState.Modified:
                        entity.OnBeforeUpdate();
                        break;
                }
            }
        }

        return base.SaveChanges();
    }

    ObjectContext UnderlyingObjectContext
    {
         get
         {
              return ((IObjectContextAdapter)this).ObjectContext;
         }
    }

    void OnObjectStateManagerChanged(object sender, CollectionChangeEventArgs e)
    {
        if (e.Action == CollectionChangeAction.Add)
        {
             //not all added entities are new
             if (UnderlyingObjectContext.ObjectStateManager
               .GetObjectStateEntry(e.Element).State == EntityState.Added)
             {
                   if (e.Element is Entity)
                   {
                       ((Entity)e.Element).OnBeforeInsert();
                   }
             }
        }
     }
}
If you are using EF 4.0 you will need to customize this accordingly.

                        
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