反序列化到子类问题

Question

我一直在尝试将一些 XML 反序列化为 class，它是另一个 class 的子 class。当我尝试反序列化到基础 class 时，它起作用了。但是，当 class 反序列化为任何子 class 时，它将失败。

我想知道为什么会这样。这是 OOP 设计违规还是我只是错过了一些东西。谢谢

代码如下：

基地 Class : Shape.cs

namespace Shape
{
    using System.Xml.Serialization;


    /// <remarks/>
    [System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.0.30319.1")]
    [System.SerializableAttribute()]
    [System.Diagnostics.DebuggerStepThroughAttribute()]
    [System.ComponentModel.DesignerCategoryAttribute("code")]
    [System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
    [System.Xml.Serialization.XmlRootAttribute(IsNullable = false)]
    [KnownType(typeof(Rectangle))]
    [KnownType(typeof(Square))]

    public partial class Shape
    {

        private string widthField;

        private string heightField;

        private string colorField;

        /// <remarks/>
        [System.Xml.Serialization.XmlElementAttribute(Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
        public string Width
        {
            get
            {
                return this.widthField;
            }
            set
            {
                this.widthField = value;
            }
        }

        /// <remarks/>
        [System.Xml.Serialization.XmlElementAttribute(Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
        public string Height
        {
            get
            {
                return this.heightField;
            }
            set
            {
                this.heightField = value;
            }
        }

        /// <remarks/>
        [System.Xml.Serialization.XmlElementAttribute(Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
        public string Color
        {
            get
            {
                return this.colorField;
            }
            set
            {
                this.colorField = value;
            }
        }
    }

    /// <remarks/>
    [System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.0.30319.1")]
    [System.SerializableAttribute()]
    [System.Diagnostics.DebuggerStepThroughAttribute()]
    [System.ComponentModel.DesignerCategoryAttribute("code")]
    [System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
    [System.Xml.Serialization.XmlRootAttribute(Namespace = "", IsNullable = false)]
    public partial class NewDataSet
    {

        private Shape[] itemsField;

        /// <remarks/>
        [System.Xml.Serialization.XmlElementAttribute("Shape")]
        public Shape[] Items
        {
            get
            {
                return this.itemsField;
            }
            set
            {
                this.itemsField = value;
            }
        }
    }
}

子class #1 : Rectangle.cs

namespace Shape
{
    public class Rectangle : Shape
    {
    }
}

子class #2 : Square.cs

namespace Shape
{
    public class Square : Shape
    {
    }
}

Class 试图将 XML 反序列化为矩形 (Subclass #1)

    string xmlSample = "<?xml version=\"1.0\" ?><Shape xmlns:xs=\"http://www.w3.org/2001/XMLSchema\"><Width>2</Width><Height>5</Height><Color>Red</Color></Shape>";
    //Shape.Shape shape = Utilities.ByteArrayToObject<Shape.Shape>(Utilities.XmlStringToBytes(xmlSample)); <-- Works OK
    Shape.Rectangle rect = Utilities.ByteArrayToObject<Shape.Rectangle>(Utilities.XmlStringToBytes(xmlSample));  //<-- Will fail

XSD 形状架构：

<?xml version="1.0" encoding="utf-8"?>
<xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
  <xs:element name="Shape">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Width" type="xs:string" minOccurs="0" />
        <xs:element name="Height" type="xs:string" minOccurs="0" />
        <xs:element name="Color" type="xs:string" minOccurs="0" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:UseCurrentLocale="true">
    <xs:complexType>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element ref="Shape" />
      </xs:choice>
    </xs:complexType>
  </xs:element>
</xs:schema>

Answer 1

转换为基类型在 C# 中被认为是安全的隐式类型转换。但反之则不然。

Answer 2

见下面的代码。我发现了很多问题。 XML 只能有一个根节点，但您有一个 Shape[] 数组作为根节点。所以我添加到您的 xml NewDataSet。类中的对象名称与 xml 中的标签不匹配。所以我将 Xml 元素添加到类。我还将 XmlAttribute 更改为 XmlElement。 Xml属性在 XML 中有一个等号。您在尖括号之间的 Xml 中有 TEXT。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Serialization;
using System.IO;
using System.Data;


namespace Shape
{
    class Program
    {
        static void Main(string[] args)
        {
            string xmlSample = "<?xml version=\"1.0\"?><NewDataSet xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"><Shape xsi:type=\"Rectangle\"><Width>2</Width><Height>5</Height><Color>Red</Color></Shape></NewDataSet>";
            StringReader reader = new StringReader(xmlSample);

            XmlSerializer xs = new XmlSerializer(typeof(NewDataSet));
            NewDataSet ds = (NewDataSet)xs.Deserialize(reader);

        }

    }
    /// <remarks/>
    [System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.0.30319.1")]
    [System.SerializableAttribute()]
    [System.Diagnostics.DebuggerStepThroughAttribute()]
    [System.ComponentModel.DesignerCategoryAttribute("code")]
    [System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
    [XmlInclude(typeof(Rectangle))]
    [XmlInclude(typeof(Square))]
    [XmlRoot("Shape")]
    public partial class Shape
    {
        private string widthField;
        private string heightField;
        private string colorField;

        /// <remarks/>
        [XmlElement("Width")]
        public string Width
        {
            get
            {
                return this.widthField;
            }
            set
            {
                this.widthField = value;
            }
        }

        /// <remarks/>
        [XmlElement("Height")]
        public string Height
        {
            get
            {
                return this.heightField;
            }
            set
            {
                this.heightField = value;
            }
        }

        /// <remarks/>
        [XmlElement("Color")]
        public string Color
        {
            get
            {
                return this.colorField;
            }
            set
            {
                this.colorField = value;
            }
        }
    }
    [XmlRoot("Rectangle")]
    public class Rectangle : Shape
    {
    }
    [XmlRoot("Square")]
    public class Square : Shape
    {
    }

    /// <remarks/>
    [System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "4.0.30319.1")]
    [System.SerializableAttribute()]
    [System.Diagnostics.DebuggerStepThroughAttribute()]
    [System.ComponentModel.DesignerCategoryAttribute("code")]
    [System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
    //[System.Xml.Serialization.XmlRootAttribute(Namespace = "", IsNullable = false)]
    [XmlRoot("NewDataSet")]
    public partial class NewDataSet
    {

        private Shape[] itemsField;

        /// <remarks/>
        [XmlElement("Shape")]
        public Shape[] Items
        {
            get
            {
                return this.itemsField;
            }
            set
            {
                this.itemsField = value;
            }
        }
    }


}

Answer 3

设法找到解决方案。解决方法是将 [XmlRoot("Shape")] 添加到子 classes 中以解决问题。

示例：

[XmlRoot("Shape")]
public class Rectangle : Shape
{ .. }

'Square' class

也一样

反序列化到子类问题

Deserializing to a subclass problems

c#

xml

xsd

xmlserializer

deserialization