XML序列化：反序列化的问题抽象属性
我现在还在环绕这整个XML序列化的事情我的大脑，而且似乎我需要一些帮助的又一次。
I am still trying to wrap my brain around this whole xml serialization thing, and it appears I am in need of some assistance yet again.
我需要能够反序列化抽象类型的属性。这种类型将被添加了许多不同的具体类型随着时间的推移，在许多不同的车型被引用，因此明确列出每个具体的类型是不是一个理想的解决方案。
I need to be able to deserialize a property of an abstract type. This type will have many different concrete types being added over time, and is referenced in a lot of different models, so explicitly listing each of the concrete types is not an ideal solution.
我已经阅读了 XML序列化和继承的类型线程，纷纷拿出有以下内容：
I have read the XML Serialization and Inherited Types thread, and have come up with the following:
<Page>
<introCommand>
<PlayElement />
</introCommand>
</Page>
**
namespace TestService
{
public class Page
{
[XmlElement("introCommand", Type = typeof(XmlCommandSerializer<AbstractCommandModel>))]
//[XmlElement(typeof(PlayElement))] **NOTE: the example works if I use this instead
public AbstractCommandModel introCommand;
}
}
**
namespace TestService
{
public class AbstractCommandModel
{
}
}
**
namespace TestService
{
public class PlayElement : AbstractCommandModel
{
}
}
**
namespace TestService
{
public class XmlCommandSerializer<AbstractCommandModel> : IXmlSerializable
{
// Override the Implicit Conversions Since the XmlSerializer
// Casts to/from the required types implicitly.
public static implicit operator AbstractCommandModel(XmlCommandSerializer<AbstractCommandModel> o)
{
return o.Data;
}
public static implicit operator XmlCommandSerializer<AbstractCommandModel>(AbstractCommandModel o)
{
return o == null ? null : new XmlCommandSerializer<AbstractCommandModel>(o);
}
private AbstractCommandModel _data;
/// <summary>
/// [Concrete] Data to be stored/is stored as XML.
/// </summary>
public AbstractCommandModel Data
{
get { return _data; }
set { _data = value; }
}
/// <summary>
/// **DO NOT USE** This is only added to enable XML Serialization.
/// </summary>
/// <remarks>DO NOT USE THIS CONSTRUCTOR</remarks>
public XmlCommandSerializer()
{
// Default Ctor (Required for Xml Serialization - DO NOT USE)
}
/// <summary>
/// Initialises the Serializer to work with the given data.
/// </summary>
/// <param name="data">Concrete Object of the AbstractCommandModel Specified.</param>
public XmlCommandSerializer(AbstractCommandModel data)
{
_data = data;
}
#region IXmlSerializable Members
public System.Xml.Schema.XmlSchema GetSchema()
{
return null; // this is fine as schema is unknown.
}
public void ReadXml(System.Xml.XmlReader reader)
{
// Cast the Data back from the Abstract Type.
string typeAttrib = reader.GetAttribute("type");
// Ensure the Type was Specified
if (typeAttrib == null)
throw new ArgumentNullException("Unable to Read Xml Data for Abstract Type '" + typeof(AbstractCommandModel).Name +
"' because no 'type' attribute was specified in the XML.");
Type type = Type.GetType(typeAttrib);
// Check the Type is Found.
if (type == null)
throw new InvalidCastException("Unable to Read Xml Data for Abstract Type '" + typeof(AbstractCommandModel).Name +
"' because the type specified in the XML was not found.");
// Check the Type is a Subclass of the AbstractCommandModel.
if (!type.IsSubclassOf(typeof(AbstractCommandModel)))
throw new InvalidCastException("Unable to Read Xml Data for Abstract Type '" + typeof(AbstractCommandModel).Name +
"' because the Type specified in the XML differs ('" + type.Name + "').");
// Read the Data, Deserializing based on the (now known) concrete type.
reader.ReadStartElement();
this.Data = (AbstractCommandModel)new
XmlSerializer(type).Deserialize(reader);
reader.ReadEndElement();
}
public void WriteXml(System.Xml.XmlWriter writer)
{
// Write the Type Name to the XML Element as an Attrib and Serialize
Type type = _data.GetType();
// BugFix: Assembly must be FQN since Types can/are external to current.
writer.WriteAttributeString("type", type.AssemblyQualifiedName);
new XmlSerializer(type).Serialize(writer, _data);
}
#endregion
}
}
然而，当我运行解串器我得到的 InvalidOperationException异常的说明的有是XML文档（3,3）中的错误。的。我已经从前面提到的线程的例子唯一改变的是类的名字。
However, when I run the deserializer I get an InvalidOperationException stating "There is an error in XML document (3,3).". The only thing I have changed from the example in the before mentioned thread is the class names.
我是在正确的轨道上吗？如果是这样，我是怎么陷入困境导致此错误？
Am I on the right track with this? If so, what did I mess up to cause this error?
从你的例子：
//[XmlElement(typeof(PlayElement))] **NOTE: the example works if I use this instead
这是推荐的方式来支持抽象类。您可以通过元素名称切换实例，并使用多个声明是这样的：
This is the recommended way to support abstract classes. You can switch instances by element name and use multiple declarations like this:
[XmlElement("playElement", typeof(PlayElement))]
[XmlElement("testElement", typeof(TestElement))]
public AbstractCommandModel Command;
当然，你还需要去掉introCommand元素或添加其他类鸟巢上面的声明之中。
Of course you will still need to drop the "introCommand" element or add another class to nest the above declaration into.
...
如果您仍然需要手动序列化，那么你在正确的道路。你的榜样作品不够好我想，这里是XML输出：
If you still need to do the serialization manually then you are on the correct path. Your example works well enough I guess, here is the XML output:
<Page>
<introCommand type="TestService.PlayElement, TestService, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
<PlayElement />
</introCommand>
</Page>
和这个XML读就好到您的对象;然而，这presents一个安全问题。任何人都可以访问修改或注入该XML到您的应用程序可以轻松地将code。
And this xml reads just fine into your object; however, this presents a security concern. Anyone with access to modify or inject this XML into your application can easily inject code.
以下是用来测试你的例子code：
The following was used to test your example code:
private static void Main()
{
StringWriter dataOut = new StringWriter();
XmlTextWriter writer = new XmlTextWriter(dataOut);
writer.Formatting = Formatting.Indented;
Page p = new Page();
p.introCommand = new PlayElement();
new XmlSerializer(typeof(Page)).Serialize(writer, p);
string xml = dataOut.ToString();
Console.WriteLine(xml);
XmlTextReader reader = new XmlTextReader(new StringReader(xml));
Page copy = (Page) new XmlSerializer(typeof (Page)).Deserialize(reader);
}