问题描述
不久,
这是一个架构
用户表
类别表
- 用户有一个 categoryID
- 我只需要用 User_ID、CategoryID、CategoryName 来填充 GridControl
- 注意,CategoryName 只属于第二个表(Category Table)
我所做的是:
Create Models (User,Category) 注意主键是复合的,所以它必须是结构 https://supportcenter.devexpress.com/ticket/details/a2615/xpo-how-to-map-persistent-objects-to-database-tables-with-compound-or-composite-multi#
// Composite key must be a struct
public struct user_key
{
[Persistent("user_brn")]
public int user_brn { get; set; }
[Persistent("user_num")]
public int user_num { get; set; }
}
[Persistent("Users")]
public class User : XPLiteObject
{
public User(Session session) : base(session) { }
[Key,Persistent]
public user_key key; // user_brn,user_num
[Persistent("user_name")]
public string user_name { get; set; }
[Persistent("CategoryID")]
public int CategoryID { get; set; }
[NonPersistent,Association("user_category")]
public Category Category
{
get; set;
}
[PersistentAlias("Category.CategoryName")]
public string CategoryName { get; set; } // I think it will work. But it doesn't
}
[Persistent("Category")]
public class Category : XPLiteObject
{
public Category(Session session) : base(session) { }
[Key,Persistent("CategoryID")]
public int CategoryID { get; set; }
[Persistent("CategoryName")]
public string CategoryName { get; set; }
private User _user;
[NonPersistent,Association("user_category")]
public User User { get; set; }
}
GridView 代码
IDataLayer dal =
XpoDefault.GetDataLayer(MSSqlConnectionProvider.GetConnectionString("
(local)","testdb"),AutoCreateOption.DatabaseAndSchema);
Session session = new Session(dal);
XPCollection collection = new XPCollection(session,typeof(User));
gridControl1.DataSource = collection;
结果:=失败
我该怎么办?任何帮助
解决方法
在您的 User
类中,删除属性 CategoryId
并更改您的 Category
属性,如下所示:
[Persistent("CategoryID")]
public Category Category
{
get; set;
}
并更改您的 CategoryName 属性:
[PersistentAlias("Category.CategoryName")]
public string CategoryName
{
get
{
return (string)EvaluateAlias(nameof(CategoryName));
}
}
从 Category
返回到 User
的引用比较棘手,因为没有持久字段来支持它。你可以免费加入试试:
[PersistentAlias("[<User>][Category = '@This.CategoryID'].Single()")]
public User User
{
get
{
return (User)EvaluateAlias(nameof(User));
}
}
,
在一对一的关系中,表应该具有相同的键。