序列化派生类型-不在数组中
本文关键字:数组 派生 类型 序列化 | 更新日期: 2023-09-27 18:11:57
通过Visual Studio设置设计器(自动生成的代码)使用.NET XmlSerializer,可以像这样序列化派生类型的数组:
[XmlArrayItem(Type = typeof(Square)), XmlArrayItem(Type = typeof(Triangle))]
public Shape[] Shapes;
...
Properties.Settings.Default.Save();
生成类似
的XML<Shape>
<Triangle>....</Triangle>
<Triangle>....</Triangle>
<Square>....</Square>
</Shape>
但是如果派生类型不在数组(或任何其他集合)中怎么办?
用XmlElement
代替XmlArrayItem
,以下
[XmlElement(Type = typeof(Square)), XmlElement(Type = typeof(Triangle))]
public Shape Window;
工作但产生
<Triangle>....</Triangle>
其中元素名是类型,而不是属性名,如果我添加第二个Shape:
[XmlElement(Type = typeof(Square)), XmlElement(Type = typeof(Triangle))]
public Shape Door;
[XmlElement(Type = typeof(Square)), XmlElement(Type = typeof(Triangle))]
public Shape Window;
序列化失败了——毕竟,在反序列化时它怎么知道哪个XML元素属于哪个属性呢?
是否缺少一个属性?我是否可以在不编写自定义序列化代码的情况下实现此功能?如何?
答案是在基类上使用XmlInclude
而不是在属性上使用XmlElement
:
[XmlInclude(typeof(Triangle))]
[XmlInclude(typeof(Square))]
public abstract class Shape
生成的XML略有不同。对于数组的情况:
<Shapes>
<Shape xsi:type="Triangle">....</Shape>
<Shape xsi:type="Triangle">....</Shape>
<Shape xsi:type="Square">....</Shape>
</Shapes>
,对于标量情况:
<Door xsi:type="Square">....</Door>
<Window xsi:type="Triangle">....</Window>
完美。
在根对象上添加[XmlInclude]
属性是一个很好的解决方案,因为它可以处理数据模型中任何地方Square
类型的多态属性的所有出现。
然而,这种情况也可以使用[XmlElement]
属性来处理,通过XmlElementAttribute.ElementName
消除多态元素的歧义:
public class Room
{
[XmlElement("DoorSquare", Type = typeof(Square)), XmlElement("DoorTriangle", Type = typeof(Triangle))]
public Shape Door { get; set; }
[XmlElement("WindowSquare", Type = typeof(Square)), XmlElement("WindowTriangle", Type = typeof(Triangle))]
public Shape Window { get; set; }
}
生成以下XML:
<Room>
<DoorTriangle />
<WindowSquare />
</Room>
样本小提琴。
复合形状序列化初稿:
[Serializable()]
[XmlRoot("shape", Namespace = "", IsNullable = false)]
public abstract class Shape {
public abstract void Draw();
[XmlAttribute("name")] public string Name { get; set; }
}
[Serializable()]
[XmlRoot("triangle", Namespace = "", IsNullable = false)]
public class Triangle : Shape {
public override void Draw() { }
}
[Serializable()]
[XmlRoot("square", Namespace = "", IsNullable = false)]
public class Square : Shape {
public override void Draw() { }
}
[Serializable()]
[XmlRoot("compositeShape", Namespace = "", IsNullable = false)]
public class CompositeShape : Shape {
[XmlElement("shape", typeof(Shape))]
[XmlElement("triangle", typeof(Triangle))]
[XmlElement("square", typeof(Square))]
[XmlElement("compositeShape", typeof(CompositeShape))]
public Shape[] Items { get; set; }
public override void Draw() { }
}
使用方式:
var shape = new CompositeShape() {
Name = "some composite shape",
Items = new Shape[] {
new CompositeShape() {
Name = "inner composite shape",
Items = new Shape[] {
new Triangle() {Name = "level 2 triangle"},
new Square() {Name="level 2 square"}
} },
new Triangle() {Name = "level 1 triangle"},
new Square() {Name="level 1 square"}
}};
// serialize ...
样本输出:<compositeShape name="some composite shape">
<compositeShape name="inner composite shape">
<triangle name="level 2 triangle" />
<square name="level 2 square" />
</compositeShape>
<triangle name="level 1 triangle" />
<square name="level 1 square" />
</compositeShape>
这种方法的缺点是,每次向层次结构中添加对象时,您都必须使用该类型的元素来修饰shape数组,因此不能真正关闭修改…