【发布时间】：2018-07-03 19:15:41
【问题描述】：
我意识到这看起来与 Using XmlSerializer to serialize derived classes 完全相同，但我不知道如何按照同一问题的指导进行操作：
using System;
using System.Text;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;
namespace xmlSerializerLab
{
public class Utf8StringWriter : System.IO.StringWriter
{
public override Encoding Encoding => Encoding.UTF8;
}
[XmlRoot(ElementName = "Query", Namespace = "http://www.opengis.net/wfs")]
public class Query
{
[XmlElement(ElementName = "Filter", Namespace = "http://www.opengis.net/ogc")]
public Filter Filter { get; set; }
}
[XmlInclude(typeof(PropertyIsOpFilter))]
[XmlInclude(typeof(PropertyIsEqualToFilter))]
[XmlInclude(typeof(OpFilterBase))]
[XmlInclude(typeof(LiteralFilter))]
[XmlInclude(typeof(Query))]
[Serializable]
public class Filter
{
[XmlElement]
public Filter And { get; set; }
}
public class PropertyIsOpFilter : Filter, IXmlSerializable
{
public Filter LeftOp { get; set; }
public Filter RightOp { get; set; }
public XmlSchema GetSchema()
{
return null;
}
public void ReadXml(XmlReader reader) { }
public void WriteXml(XmlWriter writer)
{
Program.ToXml(LeftOp, writer);
Program.ToXml(RightOp, writer);
}
}
[XmlRoot("IsEqualTo")]
public class PropertyIsEqualToFilter : PropertyIsOpFilter { }
public class OpFilterBase : Filter, IXmlSerializable
{
public string Op { get; set; }
public object Value { get; set; }
public XmlSchema GetSchema()
{
return null;
}
public void ReadXml(XmlReader reader) { }
public void WriteXml(XmlWriter writer)
{
if (!String.IsNullOrEmpty(Op))
{
writer.WriteStartElement(Op);
writer.WriteValue(Value);
writer.WriteEndElement();
}
else
{
writer.WriteValue(Value);
}
}
}
public class LiteralFilter : OpFilterBase { }
class Program
{
public static void ToXml(Object o, XmlWriter writer)
{
var inputSerializer = new XmlSerializer(o.GetType(), new Type[] {
typeof(Filter),
typeof(PropertyIsOpFilter),
typeof(PropertyIsEqualToFilter),
typeof(OpFilterBase),
typeof(LiteralFilter),
typeof(Query)
});
inputSerializer.Serialize(writer, o);
}
public static string ToXml(Object o)
{
var inputSerializer = new XmlSerializer(o.GetType());
using (var writer = new Utf8StringWriter())
{
using (var xmlWriter = new XmlTextWriter(writer))
{
ToXml(o, xmlWriter);
}
return writer.ToString();
}
}
static void Main(string[] args)
{
Filter o = new PropertyIsEqualToFilter()
{
LeftOp = new LiteralFilter()
{
Value = 1
},
RightOp = new LiteralFilter()
{
Value = 1
}
};
var query = new Query()
{
Filter = o
};
Console.WriteLine(ToXml(query));
Console.ReadLine();
}
}
}
导致这个异常：
InvalidOperationException：类型 xmlSerializerLab.PropertyIsEqualToFilter 不能用于此 语境。使用 xmlSerializerLab.PropertyIsEqualToFilter 作为 参数、返回类型或类或结构的成员、参数、 返回类型，或成员必须声明为类型 xmlSerializerLab.PropertyIsEqualToFilter（它不能是对象）。 xmlSerializerLab.PropertyIsEqualToFilter 类型的对象可能不是 用于无类型集合，例如 ArrayLists。
据我所知，我需要 PropertyIsOpFilter 和 OpFilterBase 上的 IXmlSerializable，因为我试图以this schema 描述的特定 XML 格式为目标。但我发现我还必须使 Query 类 IXmlSerializable。
这是我希望能够从模型中生成的示例 XML 文档：
<GetFeature xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
service="WFS"
version="1.1.0"
maxFeatures="0" xmlns="http://www.opengis.net/wfs">
<ResultType>Results</ResultType>
<OutputFormat>text/gml; subtype=gml/3.1.1</OutputFormat>
<Query
d2p1:srsName="EPSG:4326" xmlns:d2p1="http://www.opengis.net/ogc">
<d2p1:Filter>
<d2p1:IsEqualTo>
<d2p1:PropertyName>Prop1</d2p1:PropertyName>
<d2p1:Literal>1</d2p1:Literal>
</d2p1:IsEqualTo>
</d2p1:Filter>
</Query>
</GetFeature>
通过使 Query 类 IXmlSerializable 并编写大量的 WriteXml 和 ReadXml 逻辑，我可以让它工作，但我希望它可以工作而不必做所有这些，因为 XmlRoot 和 XmlAttribute 和 XmlElement 标记应该给出足够的信息给序列化程序，让它知道根据标签名称（匹配 ElementName）实例化哪个类，当然还有如何根据属性进行序列化。
【问题讨论】：
标签： c# xmlserializer derived-class