Question

我的表格是<条码>PolygonMapping,其登记册载有<条码>polygon id和其他有关表格的其他标语。

www.un.org/Depts/DGACM/index_french.htm

还有一个<条码>表,其登记册载有<条码>polygon_ID,它是<条码>的一部分,是<条码>点之一。缩略语

The point table contains 2 coordinates only (X and Y).

我对如何利用NHibernate为C#绘制这一数据库结构感到困惑。我愿方便地查阅<条码><><>>>>。 (因此,我认为在<条码>/条码>类别中有一个行文清单是好的,在我希望更新一个点时,我只想节省<条码>PolygonMapping。我想自动这样做。

请帮助我!

谢谢。

Answer 1

我要通过创建三个领域模型来描绘这一问题:一个点物体,一个线标,包含两个点物体,一个名为“StartPoint”和一个名为“EndPoint”的物体,另一个是含有一线数字的多角物体。域名希望:

public class Point
{
    public int Id { get; set; }
    public int XVal {get; set;}
    public int YVal {get; set;}
}

public class Line
{
    public int Id {get; set;}
    public Point StartPoint {get; set;}
    public Point EndPoint {get; set;}
}
public class Polygon
{
    public Polygon()
    {
        Lines = new HashSet<Line>();
    }
    public int Id {get; set;}
    public string Description { get; set; }
    public ICollection<Line> Lines { get; set; }
}

You could persist this class using a database schema that has a table for each domain model object.

The DDL to establish this database structure:

create table Point
(
    PointId int primary key identity(1, 1),
    XVal int,
    YVal int
)

create table Polygon
(
    PolygonId int primary key identity(1, 1),
[Description] nvarchar(255)
)

create table Line
(
    LineId int primary key identity(1, 1),
    PolygonId int foreign key references Polygon(PolygonId),
    StartPointId int foreign key references Point(PointId),
    EndPointId int foreign key references Point(PointId)
)

您的最后任务是撰写你的最佳制图文件,将域模型绘制到基础数据库表。如下所示。请注意,我将“学校”的属性定为“所有”,以满足你的要求,即拯救母体圆形物体,改变儿童物体。

  <class name="Polygon" table="Polygon" lazy="false" >
    <id name="Id" column="PolygonId">
      <generator class="identity" />
    </id>
    <property name="Description" column="Description" />
    <set name="Lines" table="Line" lazy="false" cascade="all">
      <key column="PolygonId" />
      <one-to-many class="Line"  />
    </set>
  </class>

  <class name="Line" table="Line" lazy="false">
    <id name="Id" column="LineId">
      <generator class="identity" />
    </id>
    <many-to-one name="StartPoint" column="StartPointId" class="Point" cascade="all"/>
    <many-to-one name="EndPoint" column="EndPointId" class="Point" cascade="all"/>
  </class>
</hibernate-mapping>

有了这种绘图,你就可以操纵你的母子多功能物体,在保存数据库时,整个物体图将一直保留到数据库。例如,为了在多角物体上添加一条新线,你可以使用以下代码:

        using (var session = factory.OpenSession())
        using(var tran = session.BeginTransaction())
        {
           var newPoint = session.Get<Point>(5);
           var newPoint2 = session.Get<Point>(2);
           var newLine = new Line { StartPoint = newPoint, EndPoint = newPoint2 };
            var foo2 = session.Get<Polygon>(1);
            foo2.Lines.Add(newLine);
            session.SaveOrUpdate(foo2);
            tran.Commit();
         }

Edit: The above mapping assumes that you always want to access Line objects only thru the parent Polygon object. If you want to access Lines directly, you may want to add a many-to-one reference from the Line object to the Polygon parent. To do this, you will need to add the following property to the Line class:

 public Polygon Polygon {get; set;}

此外,在线路制图档案中添加相应的绘图:

<many-to-one class="Polygon" name="Polygon" lazy="false"  />

With these changes, you should now be able to directly load a Line object that contains it s Polygon parent:

var line = session.Get<Line>(5);
var parent = line.Polygon;

Edit 2 Note that if you make the Polygon-Line association bidirectional, you will need to add code to your domain model to ensure graph consistency. See for example this SO post.

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