我有两个类,分别叫做Contact
和ContactField
。当ContactField
被添加到Contact
中时,我希望自动将SortOrder
赋值给ContactField
。我需要继承DbSet并自定义Add
方法吗?如何实现?
public class Foo {
private MyDbContext _db = new MyDbContext();
public void HelloWorld() {
Contact contact = ....; //< A contact from database.
ContactField field = ....; ///< A new field
.... ///< assign other properties into this `field`
field.FieldType = FieldType.Phone;
// How to automatically update `SortOrder`
// when adding field into `ContactFields`
contact.ContactFields.Add(field);
_db.SaveChanges();
}
}
public class Contact {
public long ContactID { get; set; }
public string DisplayName { get; set; }
public string DisplayCompany { get; set; }
public DateTime CreatedTime { get; set; }
public DateTime ModifiedTime { get; set; }
// Original codes
//public virtual ICollection<ContactField> ContactFields { get; set; }
public virtual MyList<ContactField> ContactFields { get; set; }
}
public class ContactField {
public long ContactFieldID { get; set; }
public int SortOrder { get; set; }
public int FieldType { get; set; }
public string Value { get; set; }
public string Label { get; set; }
[Column("ContactID")]
public int ContactID { get; set; }
public virtual Contact Contact { get; set; }
}
编辑:
我发现我需要监控ICollection<ContactField> ContactFields
的更改。而List<T>
是ICollection<T>
的实现。因此,我创建了一个自定义的MyList
并要求它通知MyList
容器的更改。稍后我会测试它是否有效。
public class MyList<TEntity> : List<TEntity> {
public delegate OnAddHandler(object sender, TEntity entry);
public event OnAddHandler OnAddEvent;
public new void Add(TEntity entity) {
OnAddEvent(this, entity);
base.Add(entity);
}
}
Contact
尚未保存到_db
,我能观察ICollection<ContactField> ContactFields
的Add
操作吗? - AechoLiu.Local
会将整个表从数据库加载到内存中。即使是中等大小的表也会对性能产生巨大影响! - Breeze