On Insert / Update logic in EF code first

问题

I would like to add some logic to the insert and update events of some EF objects. I have a MVC application with category object which has a property which is a slugified version of the name property.

public class Category
{

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

I would like to set the UrlName property only on the insert and update events because my slugify logic is quite elaborate.

I am aware that I can add some logic inside the SaveChanges() function on the context itself but I rather would like to put the code closer to the entity itself.

Is there a way to accomplish such thing using EF code first?

回答1:

You can setup a base class with methods to be called before insert and update

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

    public override int SaveChanges()
    {
        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();
    }

回答2:

No there is no such extension point because your entity is POCO - it is not aware of its persistence. Such logic must be triggered in data access layer which is aware of persistence. DbContext API offers only overriding of SaveChanges.

You can expose custom events or methods on your entities and call them during processing in SaveChanges.

来源：https://stackoverflow.com/questions/7041178/on-insert-update-logic-in-ef-code-first