使用IXmlSerializable的问题

昵称10504424 2013-10-30

展开全文

最近又开始使用XML了，但今天遇到一个折腾我一下午加一个晚上的时间，终于从网络上找到相关的资料解决了。

有一个成员是用来存放正则表达式的，由于里面包含其它字符，所以想用CDATA来保存方便查看，所以想到另建一个类再通过继承IXmlSerializable 接口来实现CDATA节点。参照了官方MSDN文档，写了类似以下的代码：

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using System; 
using System.Xml; 
using System.Xml.Schema; 
using System.Xml.Serialization; 
using Microsoft.VisualStudio.TestTools.UnitTesting; 
using System.IO; 
using System.Diagnostics; 
  
namespace BeiBei.Core.Tests 
{ 
    [XmlRoot("Worker")] 
    public class Worker 
    { 
        [XmlElement] 
        public string JobTitle { get; set; } 
  
        [XmlAttribute("active")] 
        public bool Active { get; set; } 
  
        [XmlElement] 
        public string NextPageEncodingName { get; set; } 
  
        [XmlElement] 
        public Person Person { get; set; } 
  
        [XmlElement] 
        public Person Person2 { get; set; } 
  
    } 
  
    public class Person : IXmlSerializable 
    { 
        // Private state 
        private string personName; 
  
  
        // Constructors 
        public Person(string name) 
        { 
            personName = name; 
        } 
  
        public Person() 
        { 
            personName = null; 
        } 
  
  
        // Xml Serialization Infrastructure 
        public void WriteXml(XmlWriter writer) 
        { 
            writer.WriteString(personName); 
        } 
  
        public void ReadXml(XmlReader reader) 
        { 
             personName = reader.ReadString(); 
        } 
  
        public XmlSchema GetSchema() 
        { 
            return (null); 
        } 
  
  
        // Print 
        public override string ToString() 
        { 
            return (personName); 
        } 
  
    } 
  
    [TestClass] 
    public class IXmlSerializableTests 
    { 
        [TestMethod] 
        public void S_Person_Test() 
        { 
            var p = new Person("Shawn"); 
  
            XmlSerializer serializer = new XmlSerializer(typeof(Person)); 
  
            string path = "D:\\Test.Person.xml"; 
            string path2 = "D:\\Test.Person.2.xml"; 
  
            using (var writer = XmlWriter.Create(path)) 
            { 
                serializer.Serialize(writer, p); 
            } 
  
            using (var reader = XmlReader.Create(path)) 
            { 
                var p2 = serializer.Deserialize(reader) as Person; 
  
                using (var writer2 = XmlWriter.Create(path2)) 
                { 
                    serializer.Serialize(writer2, p2); 
                } 
            } 
  
            var xml1 = File.ReadAllText(path); 
            var xml2 = File.ReadAllText(path2); 
            Assert.AreEqual(xml1, xml2); 
            Debug.WriteLine(xml2); 
        } 
  
        [TestMethod] 
        public void S_Worker_Test() 
        { 
            var p = new Person("Shawn"); 
            var pp = new Person("John"); 
  
            var w = new Worker() 
            { 
                JobTitle = "Boss", 
                Person = p, 
                Person2 = pp, 
                NextPageEncodingName = "gb2312", 
            }; 
  
            XmlSerializer serializer = new XmlSerializer(typeof(Worker)); 
  
            string path = "D:\\Test.Worker.xml"; 
            string path2 = "D:\\Test.Worker.2.xml"; 
  
            using (var writer = XmlWriter.Create(path)) 
            { 
                serializer.Serialize(writer, w); 
            } 
  
            using (var reader = XmlReader.Create(path)) 
            { 
                var w2 = serializer.Deserialize(reader) as Worker; 
  
                using (var writer2 = XmlWriter.Create(path2)) 
                { 
                    serializer.Serialize(writer2, w2); 
                } 
            } 
  
            var xml1 = File.ReadAllText(path); 
            var xml2 = File.ReadAllText(path2); 
  
            Debug.WriteLine(xml2); 
            Assert.AreEqual(xml1, xml2); 
        } 
    } 
}

　　结果Serialize出来的文件是正常的，但Deserialize后文件中，第一个Person之后的其它属性都没有了。

尝试了很多次，当个PERSON对象序列化/反序列化都是没有问题的，但当对象包括PERSON，且PERSON属性后还定义了其它的属性，尝试添加<XmlElement>之类的特性都没用。结论就是：第一个PERSON属性之后的其它属性一率都没能正常Deserialize。怪自己对这块不了解，更怪MSDN没有写好例子！

后来在这里找到答案：

http://www./Articles/43237/How-to-Implement-IXmlSerializable-Correctly

其实跟属性顺序没有关系，而是我们没有把ReadXml的实现正确地实现了。再改成如下就正常了:

public void ReadXml(XmlReader reader) 
{ 
    reader.MoveToContent(); 
    var isEmptyElement = reader.IsEmptyElement; 
    reader.ReadStartElement(); 
 
    if (!isEmptyElement) 
    { 
        personName = reader.ReadString(); 
        reader.ReadEndElement(); 
    } 
}